Game mode idea where you can play as any two champs via a "Tag" summoner (Engine allows for this)

In the tutorial there's a feature in which you can swap your champ on the fly by going to an alter

Ok so if that can happen then that function can be bound to either a summoner spell slot or your boots (Start at level 1 with a pair of basic boots)

here's how it would work.

Pick type: Draft with bans, you would take two turns, have one set of runes not two so you'd want something that overlaps and functions between the champions, everyone sees what champs you pick.

Item pools: You would only have one set of items, this would encourage strange builds that function between your two choices, and would naturally function as a gating mechanism against the more extreme combos

If coding allows for it then maybe you would share the top three items in your backpack, but the lower three would be distinct, but this would create questions on gold income.

Health and stats: You would have base stats that are the average of both chosen champions, Your health pool would be shared, resource pool would be shared if applicable, if champs rely on separate resources then you swap when you swap champs.

Passives: This would be a good type of charm to the mode, having passives overlap/stack. Secondary passives, such as passives on abilies could also stack. From crazy things like taric+malphite double armor buff, to even crazier things like vayne+gnar W

Cooldown: the switch option would baseline at 20 seconds for level 1 down to 10 seconds at level 18, it would be affected by either CDR or Attack speed, up to a cap of 40% cooldown reduction

Teams: Option A. two teams, hexakill format just for keks on sum rift play for nexus Option B. 12 man duos battle royale, so you and 11 other dudes, everyone has a teammate, ascension map for points/kills