Have you ever played a game of Stellaris, the year is 2400+, you out-tech everyone else in the galaxy by a huge margin, sitting on your ringworlds, literally swimming in resources, and thought to yourself "Damn, I wish my ships looked high tech and enigmatic to fit my RP style of being a Fallen Empire wannabe"? I did and I think it would be great if we could transform our ship models to a more advanced version somewhere late-game. Maybe it could be a special project, bonus for certain ascension perks such as "Galactic Wonders" or "Enigmatic Engineering"? Or do it automaticaly once certain technologies have been discovered such as Dark Matter Reactors, etc. Definitely not a gameplay changer, but would add some flavour and feeling of "being a unique special snowflake". Obviously, Paradox would not do it for free but as part of future expansion, DLC, maybe? Mowing down enemy fleets with your 10k battleships like it's nothing is fun. But feels even better if your ships look like something from another galaxy.