I don't like the generic bonus actions because many players will spend time on their turn looking for some way to use that bonus action. Actually I hate bonus actions in general because players do this during character creation (many players try to make sure every character they build has some use for the bonus action, such as an extra attack or spell effect) and also because bonus actions are confusing.
I like the idea of generic reactions because I think doing things when it's not your turn is a lot of fun. It gives a player something to do other than just watch.
Here's generic reactions I've used in the past:
- When forced movement would push you off a cliff, you can use your reaction to fall prone on top of the cliff, and not fall off.
- When an object within 5 feet of you changes, you can use your reaction to interact with that object (e.g., a door flies open next to you, you can use your reaction to close it again; or someone drops a weapon, you can use your reaction to pick it up)
Here's a generic reaction I'd like to introduce as a house rule maybe: When you get attacked or make a Dexterity saving throw, you can use your reaction to take the Dodge action (and it applies to the triggering effect) but become incapacitated until the end of your next turn. (Basically, you would give up your next turn, in order to haul ass right NOW.)