There are plenty of fan proposals what those lesser ships could look like, so I don't really see the big loss you are trying to propagate.
Why, your attempt to evict the one canonical, onscreen example of such in the movies from existence!
Are you going to categorically stamp out the fan vessels next or what?
What we see in ST III is the Federation Survey Vessel Grissom
, which apparently may have a untold back story.
So I can't see how extending
an existence qualifies as evicting
an existence. That's a contradiction. Maybe you should sleep things over, at least that's what I'm going to do now.