The only things I can think you are missing is the Academy live-fire range (starship), in an unused portion of the asteroid belt. The Pluto (orbit or what I don't know) communications relay station (both are from the SFA box set). Oh, lets not forget the Mars Perimeter Defense Network.
Also some minor details about the system arrangement.
---Inhabited Planets: Venus (Sol II [Class k]); Earth (Sol III [Class M]); Luna (Sol III a [Class F]); Mars (Sol IV [Class H]); Titan (Sol VI f [Class G]).
---Other Planets: Six others, including two gas giants.
last I checked there are 9 planets in the Sol system (10 in Trek apparently) and 4 of them are gas giants, Jupiter, Saturn, Neptune, and Uranus...not the two you mentioned.
By the way, I like the B5 ref. on Mars, but by this point don't you think she might be a little bit more on the inhabitable side? Class L or something.
Phoenix...
"I'm not saying there should be capital punishment for stupidity,
but maybe we should just remove all the safety lables and let nature take it's course"
"A Place For Everything & Nothing In It's Place"