Catch=candy battle=stardust

Would it be difficult or would it break the game if we had the option of instead of catching a wild mon fighting it instead. Instead of receiving candy receive double stardust from defeated mon?
Obviously this would mean people would meatgrind every mon in sight with their lvl 30 dragonite or machamp .. though could make an in game "anti poaching wtf law" which means you cant battle a wild mon with a mon that has higher cp or something. Ie. Youd need to fight a cp150 pidgey with a mon that had less than 150cp for example. Beat it and you get 200 stardust instead of 100, if it defeats your mon it runs away to lick its wounds... increase chance to flee midfight once its below 30% hp or something. I dont know. Would certainly add a bit of variety to the game and battling with low lvl mons and not just high lvl ones for raids would make a use for those 20hp potions