Truthfully, I'm less fussed about the bonus action spell limitation rule being ignored. Every DM I know and play with ignores it and considers it arbitrary and pointless.
There are no breaks or abuses that emerge as a result of not having the rule, that are not exceeded by other perfectly legal alternatives, or paid for in adequate balance cost, with the sole exception of Quicken meta-magic. Quicken meta-magc deserves to have the bonus action spell limitation applied to it; every other spell-caster everywhere else does not. (There's an easy rewrite for the quicken meta-magic specifically, that uses similar wording to denote that when you use this meta magic to cast a spell as a bonus action, you can only use your action to cast another spell if that spell is a cantrip)
There are only a limited number of bonus action spells, and a large swathe of them are spells designed to be coupled with the player taking the attack action - they're ranger and paladin spells. For the rest, there aren't any breaks or abuses that show up, even if you scan the entire list of BA spells in the current game.
