Shove better stay a bonus action.
people whining about this are insane, Shove is a terrible waste of an action, if you get done in by a bonus action tis your own fault for not positioning correctly...
This has already been discussed at depth in other threads, but some issues with your above are:
a.) BG3 shove distance is too far. You don't actually be need to be adjacent to a ledge to be shoved off. If two enemies decide to shove you back-to-back, then it's incredibly hard to put yourself at a position where you won't end up flying off a ledge.
b.) The prevalence of insta-death pits. Are you saying that a single action is too costly for something that can be a OHKO?
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As for Ready Action. Larian could do that, or honestly just put in a Delay action. Even though it's not available in 5e, it's close enough to Ready and should be simple to implement given that it existed in DOSII.
