I have been playing KSP since before it had planets. But as soon as it had planets, you know the community started modding realistic size Earth in. Many love the bigger challenge and the sense of home.
With KSP2, there will be multiple star systems. So my really obvious take is, why not just make one of those systems our solar system. It does not have to be populated or even 100% accurate. I think many players will jump at the chance to "discover" Earth and launch from there. I realize it won't be a quick or easy to implement. But if you already have the tools. I would say why not go with the obvious choice and add something most players would love.
As for the realistic rockets. I'm sure that's a different discussion all together, though the procedural parts may just scratch that itch anyway.