Multi account advantages, ideas to even it out?

I'll go through your ideas one by one.

- Utterly absurd and defeats the whole point of lvl 4/5 raids

- LOL. i'm all for bonus rewards for completing tasks but you just want an easy source of rare candies and legendary rewards there.

- Isn't it easy enough to take down gyms already? Feeding gyms is the only way to hold onto them when someone is attacking.

- Pointless. A multi account user can still do 50 trades in the morning, 50 in the afternoon, 50 in the evening

- IV's are already randomized when trading, so you can't simply trade over a 100% pokemon. Most people use multi accounts to support their main account in raids and get more shinies. They don't use them to collect more 100% pokemon.

- Decent idea, except the gotcha users will then start raging. Gotcha users essentially pay money to be allowed to cheat, which i don't agree with but that's a different story.

Like it or not, multi account users give Niantic more money. I expect traded pokemon will be banned from PvP when it arrives. That will totally kill any advantages of multi accounting there.

I consider the disadvantage of having to manage several accounts enough of an incentive to not have them. It's clumsy to hold two phones and play, impossible to catch pokemon efficiently with both and hitting the trade limit by yourself equals 3-4 evo sessions with two phones. I'll put the effort into my one account.

I like the feeding limit suggestion. I think it's ridiculous that a multiaccounter or an organized group of remote players can prevent the takedown of a gym by a player who is physically there. It's an AR game and the person who's physically at the location should be the one who's advantaged. In Ingress you can guaranteed take any portal if you're there and the opponent isn't, the most the opponent can do is force you to use more resources and a bit of time, and it makes for a much healthier competitive experience. Unfortunately, need for GRB makes Niantic money so we aren't likely to see any nerfs to remote feeding.

The only realistic approach is to make accounts more meaningful for the high level players. The fact that they ran out of stuff to do is obvious when people start caring about the "extra xp" over the 40 level limit. It must be boring for a level 40 trainer who pretty much has caught them all

The level limit will certainly be reworked. Cause it's a change that will give niantic profit and help them maintain their playerbase. What I want to see is some sort of new feature added, something like legendary challenges/quests/fights/whatever that refresh every so often and are hard to do. It doesn't need any absurdly good reward like you are proposing, it just needs to be there as a feature that a max level player is looking forward to try to accomplish every week.

And yeah, like housunkannatin said, managing 2 accounts is already enough of an incentive towards having a single account.

Once you've hit 40, done everything, there's nothing to give you a rush for the months between gens, bar day 1 of a brand new raid boss. No new mon. No sense of completion. That's enough of an incentive to start one: "wow! I finally got a [reasonably rare in the wild evolution]" retriggers that reward feeling.

I don't have a 2nd account, but I get a little thrill when my kids find something new. This weekend it was wild Ninetales, which they needed. (I'm at 375/377 and they're at 295/344)

To me, the root causes are:
1. Niantic trying too hard to push PoGo as a social game, but with limited social features.
2. Broken mechanics, glitches and unfair design that make cheating widely seen as acceptable.

The community tried to get around 1 with raid maps and social media groups, but Niantic destroyed the former, while the latter were prone to bullying and abuse.

Remote feeding should just be abolished. You want to defend your gym? Be there. Otherwise, tough. This was never a "thing" before the gym rework, so it's not like Niantic would be gutting tradition by getting rid of it.

IMO Niantic already found a way to balance multi accounts: stardust.
You can do all those things you mention in your list, but for many pokemon you raid, catch or trade you still need millions of stardust to power them up and actually use them. Plus millions stardust to trade shiny. You also need the coins to increase bag space, etc. And in summary, a lot of time to maintain the accounts operative. It's already hard to keep up with the maintenance of a single account, double time and effort for a second...and scalate for any number of accounts you can imagine.

Soloing 4-5 Raids: No. BAD Suggestion. Bad bad bad. Entirely defeats the purpose of having a tier system for raiding if you can do any of them on your own.

Better Fix: Make some of the useful Pokemon ONLY available through Raids. Right now, that is limited to Absol - and even Absol is not that useful of a Pokemon. Mawlie and Alolan Marowak are really fun, but utterly useless.
-Not sure what Pokémon would apply for this from Gen 4 and onward; if I were to go back to the beginning, then Pokémon like Lapras and Snorlax would be in there, as well as potentially any Pokémon with no Evolution tree at the time, like Onix, Magmar, Electbuzz, Tangela, Chansey, Jynx, Porygon, etc. They wouldn't be available from Eggs until their Baby forms were released, and if they don't have Baby forms, then they are only available via Raiding and Trading
-Introduce a 10km Buddy Distance for these Pokémon to "encourage" Raiding them instead of walking them for Candies.

Another Fix: Make it so you need to "Defeat" a Pokemon in order to evolve it. For example, if you want a Gallade you have to beat it as a Kirlia. (which wouldn't work NOW, of course, just using that as an example)
-Make it so that a Pokemon needs a certain number of "Victories" in order to Evolve; using the Gallade example, make it so the Kirlia has to beat a certain number of opponents before it is ready to Evolve, and have it so every Kirlia who takes part in a Raid Battle gains a Victory, even if they faint before the final blow. This would make it worthwhile for players to hop on an AM raid to boost the amount of Victories their Kirlia has, and bring them closer to Evolving.

Active Play Rewards: Already got them - Research Tasks.

Feeding Gyms: Any solution that limits the players able to be feeding would be too complicated to implement and would be easily abused by Multi-Accounters. I have 2 accounts, I attack with two accounts - but I immediately run away with one account. How many accounts can defend now? I've got a Pokémon in the gym but only have a few GR's, and I see it first - I put on 2 GR's and wash my hands of it. How long until you can feed it a GR, because you want to defend it for longer? If there's an error or a cool down between which defenders can feed GR's, then the attacker is going to win. It's too much hassle for next to no benefit.

Better Fix: Gym Rework. Full tear-down and rebuild. The Gym system has always been the weakest part of Pokemon Go, and it's the one area that they consistently get wrong. It's going to take another full change to the Gym system, or two, or three, or nine, and it doesn't particularly matter if players have multi-accounts or not.

Trading Cooldown: Meh. Niantic has toned down the Lucky rates a great deal - something like 1/40 now, or even more rare (I've only gotten 1 Lucky Pokemon in my last 50ish trades, for example. A level 17 Abra that I traded with someone for an Alolan Vulpix, since they were new and had nothing I really wanted), so it would take wasting a LOT of good Pokemon before getting a Lucky. Not to mention that if you aren't Best Friends, it is almost guaranteed that the IV's for the Pokemon after the trade will be worse than before. (Just not as bad for Ultra Friends and it would be for Good Friends) And trading for Shiny's is great... except that Shiny's have no benefit, and cost a hell of a lot to get that new Shiny. Even for Best Friends, it's what - 40,000 Stardust for a new Shiny? If players want to waste 40,000 Stardust on two accounts for a Pokemon that is merely cosmetically different, have at it folks!

Level/IV/Weight: ...what? This point confuses me because "Weight" is utterly pointless in the game, Shininess is likewise pointless, while Level and IV are extremely important. I'm assuming you mean that you, Level 40 Trainer, and I, Level 4 trainer, never catch the same Pokémon? So if I catch a 100% Pokémon in the Wild, no one else can catch it because it's randomized? That would remove a rather significant motivation for many players to play the game as it removes the chance for catching a known 100% Pokémon - and a lot of players have that as a goal. It would take one of the few actually useful Social Aspects of the game - communicating the location of a specific Pokémon - out of the game, and would only lessen the game.

Lower catch rate/lower flee rate: Gotcha Abuse? How is this abused? Does Gotcha give a higher rate of catching than a GoPlus? Does Gotcha do Curveballs? Use Berries? Get Nice/Great/Excellent throws? How does one abuse a Gotcha?

I used to use a GoPlus. I stopped using it to catch Pokémon after Weather Boosts came out because my catch rate dropped from about 40% down to below 25%, and I just didn't care to waste that many Red Balls. So unless the catch rate has been upped on the Gotcha somehow, I don't see how there can be any significant abuse of a Gotcha/GoPlus.