I think as long as it doesn't feel like they are changing things just because they can, they should do it where it makes sense.
I mean there's no reason Nora Satie would arrive in an Oberth- I say be bold and make it a Nebula or Ambassador.
Refits and cool new angles should do the trick in 80% of cases though.
But what they could do is add new ships in the background- when they are near a starbase for example. It would also be nice to get a view of Walker Keel's ship in orbit.
A totally different case are freighters. Now it makes sense that some freighter models would be in use in different fleets, and for a long period of time- that's why I would like to keep the ST3 freighter reuses in some cases.
But even there, they could play around a bit, with different versions of that freighter, slightly refitted and sometimes patched together with other parts.
But that also means where it makes little sense- like with the Sheliak vessel- they shouldn't be afraid to make new designs. Another case where a reuse doesn't make much sense is the reuse of the Talarian Warship, as cool as it looks.
Not sure about the Pakled ship reused as the Acamarian Gatherer's ship. The Gatherers could have stolen it from the Pakleds or vice versa.
I think the toxic watse ship in Final Mission was also a reuse- so I would appreciate some changes there as well because that vessel was supposed to be ancient.