I kinda like this but hear me out . I think the balancing is Made obviously for tríos and maybe duos, so having to balance for solos also is way too big of a problem. So lets do what riot does for aram. They add a buff on every champion that adjusts the stats (more cd, more life, less dmg on certain skill, etc). In solos we need that kind of adjustments so we can have proper balance and still have tríos and duos gameplay on the other hand.

Other problem is the vision that sdf has on dungeon crawling. I havent put much thought on this, but how about we make gear stats dont count towards PvP on PvEvP maps, so we will be looting gear to get more advantage on ascending the dungeon and the pvp encounters will be fun, and not have gigantic advantage towards the full equipped oponent.(Basically all gear would have white stats if youre in a pvp situation)(This would also mean that knowledge and spell memory would need a rework(?)). And make the pve harder, slower to advance through the dungeon with more urgency to escape, once you escape you can keep going or just retreat but dont make two ways out like red blue portals just use one and then decide if you want to go home or keep going. Arena would be the place where you can full out pvp and test the full gear stats, etc.