How are Sentinels and skyscraper promos going to work?

Base powers would be on alternate character cards, which are permitted.

Tiny Chiwawas - Until the beginning of your next turn, whenever a target enters play, deal 5 sonic damage to each target.

to powerful, 1 damage more likely, especially since there is already a couple of similar cards in the game

You've clearly never heard a chihuahua.

Incapacitated ability for Tiny Chiwawas form: Until the start of your next turn, whenever a target deals another target melee damage, deal each target 1 sonic damage.