Great suggestions!
I will confess that I'm currently creating this mod while playing, unblocking myself as I go. I haven't gone to all the planets yet, so I'll have to get there before I can test modding them.
Space Age - for me - has felt like a bunch of mini games but you always want to "go back home" to Nauvis. With this mindset, the excursions should be simple enough to complete and then allow travel back again. I we'd include angel ores in space, that would explode the complexity and size of space ships. You would probably build a huge space base, equally complex as you main base on Nauvis - This would turn into another Sea/Space Block.
I think the original Space Age was designed so that you are not expected to have any meaningful production in space, except for a few select items. We don't want to move all production up into space.