I’m not certain how familiar people here are with No Man’s Sky content creators on YouTube but one such person is “Professor Cynical”. The title of the video is “Amazing Features Hidden in Worlds Part II Game Files”. Whenever Hello Games puts out an update they always seem to include features for future updates that are not activated. Modders can activate these features. Now bear in mind this feature is VERY rudimentary at the moment. But essentially your ship can be a functional base which you can build or add stuff too. You can add a hydroponic tray to your ship and if you launch your ship and fly around, the hydroponic tray goes with your ship. So this tells me Hello Games is working on modular ship building probably very similar to the modular ship building in the game Starfield by the company Bethesda. I’m already imagining in my head what this is going to be like. This doesn’t mean though that the feature will actually see the light of day. If this feature is implemented, Hello Games has to introduce a new class of starship which we would simply call a modular ship. And this would be a ship you can control and fly around with AND also walk into. Basically, you can create a mobile base. Hello Games kept all of the current systems the same and implemented the new terrain generation simply by adding a new class of star system, namely the “purple” star system. So I think Hello Games will keep all current ships just as they are. Haulers are huge and it would be nice if you could walk into them but I think Hello Games would keep haulers just the way they are now. If you want a ship you could walk into, it would have to be a modular ship.
The boys and girls in the datamining labs posted some findings and sciencings on what’s currently in the game code and got a prototype up and running.
If you don’t mind peeking in there, you can see their findings discussed and demonstrated in the datamining thread 
it’s very exciting stuff indeed 
I’ve already mentioned in the data mining thread that the mentions of “corvettes” in the data and an aparently experimental capability to attach bases to starships most likely indicates that HG is playing with the concept of flyable ships that allow for at least some interior decorating. How fervently this feature is pursued and when it would arrive in production is an entirely different question, though.
This could be limited to the Corvette ship that is in game files or it might be for all starships. I’m kind of nonplussed about adding stuff like hydroponic trays to a solo pilot starship.