+1 for a Ready Action system, and an Overwatch system is a decent enough implementation of it.
You would tell your DM if X happens do this action at the cost of using your (bonus) action for the current turn.
Clarification: You use your Action to Ready something, and then your Reaction if/when the trigger happens. RAW you can't ready a bonus action, though I imagine many games homebrew that you can.
(Still would love more option beside overwatch: to ready an action for feathered fall and automatically trigger it if one of my companion get pushed)
If readying Feather Fall costs both your action and reaction, then it'll have been made
much less powerful, to the point of almost uselessness. The whole point of Feather Fall is that it
only takes your reaction and you don't have to attempt to cast it in advance. Having to spend an Action to precast it, just for the possibility you might need it in the next turn, is very punishing. It should simply be a toggle that activates whenever you or an ally gets pushed off a cliff (ideally with a prompt imo).
