Crowned
Metagame Premise: In this Metagame, a “Crown” spawns on the first turn for the player that sends out the slowest Pokemon. The Crown will give that trainer a x1.2 Omni-boost to their Pokemon, but if the player with the Crown uses a move with Effective 60 BP or more, they pass the Crown to their opponent.
Potential Bans and Threats:

Slow Pokemon are king in this meta (literally). For the first few turns at least. While there is some nuanced in what you want to send out as your lead, Pokemon that are slower will be far more useful.
Additionally Pokemon that focus less on offensive output will be more desirable.

Other desirable traits will be Pokemon that learn low BP moves with strong utility. If you want to keep your Crown, you got to use weaker moves. And technically moves like Mortal Spin, Rapid Spin, and Nuzzle full under that category.

(or would have, rather)
To clear things up, Multi-hit moves will count as having more than 60 BP if their maximum hit causes the move to have a BP effectively that high. So for example, Icicle Spear has 25 BP, but is effectively 125 BP after all 5 hits land. Meaning that using Icicle Spear will still pass your crown to your opponent.
Questions:
-Should the numbers be tweaked? I just picked <60 BP and x1.2 boosts as they seem pretty modest. Let me know if the BP limit should change, or if the stat boost should change.
-Additionally let me know if you’d prefer the Crown to provide some other benefit (like passive healing or something) or if there should be another method to pass the crown.
-Also, how do you feel about who gets the Crown first? The simplest idea I came up with is giving it to the slower Pokemon on turn 1. The idea is that the slower Pokemon is already disadvantaged so can be compensated with a Crown.
Another idea is giving it to the Pokemon with the lower BST too, though things get complicated with speed ties.