To reduce travel times and, more importantly, the number of loading screens people will see on average I would like to propose that the Sol system is added to the Alpha Centauri Sector Block. While ideally the various directly adjacent sector blocks would eventually be conglomerated into a single larger 'world map' that is more of a longer term adjustment to the game. This proposed change is something I think is more likely to be made possible either in the short or mid-term.
And there won't be a whole lot of times that you'll need to return to Sol after you get to higher levels...
The problem with transwarp is that, at the moment, you have to wait a half hour before using it again, which could potentially become quite inconvenient.
Also, Starbase One has a few features that nowhere else has, including the ship purchasing NPC. You can't do it anywhere else, except for the Runabout on DS9.
Besides, given the way the galaxy map looks and how the Sol System is centrally placed between what I assume will eventually be four sector blocks, it only makes sense that you can access it from any of those four.