Slaking would likely require gyms to be completely overhauled. CP dictating placement in a gym is dumb and discourages teamwork and diversity. I would love for pokemon like Ampharos, Umbreon, and Steelix be able to shine on defense despite their below-average max CP.
Secondly, Slaking would need to attack twice as slowly on offense and defense similarly to Ditto. Meaning on defense, it would only attack once every three seconds.
CP is dumb because attack is weighted more in the formula, so good gym defenders are punished for having high stats that are actually useful in defending (defence and stamina) while pokemon with weaker defending ability top gyms.
The CP formula can be changed without altering the base stats of any Pokemon. If stamina had higher weighting then annoying tanky Pokemon that take longer to beat would sit higher in gyms while glass cannons would sit lower in gyms, but battling would still be the same because stats are unchanged.
This way people can't just power up attacking Pokemon and then dump them in gyms anyway just because of their high CP.
Blissey and Snorlax are the exceptions because their stamina values are so insanely high that they still manage to get high max CP, but there are plenty of good defenders that barely have 2500 max CP.
Yeah cp isn't a reflection of the in-game stats. Blissey had a base stat of 200+ for special defense and 10 for defense.
Mew and Dragonite have the same base TOTAL (600) but Dragonite, due to a higher attack, pans out 450+ cp greater than mew.
And cp is Niantic's perception of usability of pokemon within the original games (in my opinion)...which is a poor reflection. Umbreon, a mon that just hits over 2000 cp, is a taaaaank and performs significantly better than espeon in many situations in the main series [stall wars let's goooo]
Slaking isn't a psuedo legendary though! lol I agree, but we'll see. Blissey will be laughable compared to Slaking who is an absolute monster. I hope the spawn rate of those is so rare they only appear in a city 1x a week at super low levels so you have to walk w/ it to power it up.