Almost every 'space' within ED is an instance, also a number of the ships basically cannot work as they are, with navigable interiors that are connected to external access, as that all then has to work with the highly-instanced model Frontier use, never mind that virtually all ships will have constraints around where things are placed. Vast majority of ships have entirely missing interiors, many of which would require fundamental rework (where SRVs sit, where fighter bays sit, cargo, living, entrances, everything really) because at present none of it matters as it's not presented to the player.
I get the allure of having Star Citizen like 'Neil Armstrong' moments in ED. However the game is not built to facilitate this, majority of ship designs are literally a decade old and space legs was not a thing to plan for (the textures for some ships sure have not aged well, either, and do not start me on the state of the really, really poor quality of ship paints at this point.. argh!) .. and I am not sure Frontier would want to consume the time, resources and people to achieve it.
Frontier could make the entries to ships interactive in the sense of having lifts for the large ships (SRV could have an animation that vaults us into the chair for example) and have the various ship stairs connect to an interact-able 'door' that then does the instance/ seat switch -- to at least create the sense we're able to ingress and egress somewhat like normal people -- but I think people will always, always want the whole SC seamless experience for ships (and other spaces), and I am not sure the developer has the time, inclination or resources to add literal years of work to the pipeline for it, even if the engine could in principle be re-engineered to do at least some of it.
There are things Frontier can do and (after coming out of a state of sleep paralyses) are doing, which is not something I thought I would see in the year of our lord, 2024, but I think the whole FPS first ability to access ships and the world at large, requires a fundamentally different approach, and ED may stop being the ED a lot of people like in the process. Something not lost on Frontier, I am sure.