Champions online, and nominally uses the same engine as STO. In champions a vast ground map spans levelling zones for 1-20, 10-20 and 20-30 and contains a seamless social / crafting hub, with a specialist training area where you can go to train your character to level up and you are not charged any skill points until you leave.
Now, STO has more complication - we frequently transition between ground and space so the content is all very fragmentary.
But, it would potentially go a very long way to improved immersion if at least a select few ground maps could be extended to include this kind of concept. The Academy, Vulcan, Qo'nos, New Romulus, Bajor could all benefit from feeling more planetary, and we could re-locate the event holidays and festivals to take place on these maps rather than having specific instances only at certain times of year.
Risa is almost there, but I'm confused by the continued existence of old-risa which is really pokey and not fun at all to visit.
Also, even as a long term player, I don't even know where all the available social maps are - both fully public and fleet.