I really, really don't want the game to freeze just when a Paladin's attack is about to connect to prompt for Divine Smite.

If they will do reactions as proper reactions / prompts, they should convert as many reactions as they can into active ones, Divine Smite being a good example. >> Charge the weapon as a Free Action until it lands a hit and discharges. Almost the same mechanically but not the massive pain in the ass to use that a constantly appearing prompt that pauses the game at the worst possible moment would be.