Bro it is not too late for HTML emails. After all Q2A doesn't have this feature and everyone would definitely need this. It improves the user interaction with the email and thus giving more and more of returning users.
Secondly, you say either it should be in a plugin or in core. I would say this should be in core as Q2A core is lagging much behind adding those features which are needed by most users will only make it better. But if you do that through a plugin then it would again add one more plugin to an already too big plugin list on our websites.
Contributing to core through pull requests for this feature will be the best. But I can be wrong so let's see what others have to say.