Cmcastl - There comes a point when you realize that for whatever reason that someone else isn't going to 'do something' and you have a choice to make: live with the situation 'as-is' or do it yourself.
During a beta or maybe the first release I wanted a lot more ship diversity, but Deanej liked having the Light I, II, and so on, but he pointed me in the direction to make the changes I wanted. Now many of the races have multiple ships, with the Federation especially having Miranda Class, Constitution Class, Galaxy and so on. This is a minor change to what you are discussing, but it's just an example.
I admire your desire for what you see as an enhancement to the mod, but I can say that to really implement ground forces and to get them to work and work well (the AI would be the major issue) would take much more time than anyone in the position of making it happen is willing to do. I think at this point if it's going to happen, your going to have to make it happen. If I had the desire, the free time of which I have nearly zero now, and the ability to implement a true ground force option I think it could be interesting.
Honestly though, the most I might do when I do have the free time will be adding the transport ships like I've discussed before.
What I can say from personal experience is this: in the Civ III Star Trek mod, ground forces didn't work really well for several reasons. In one game, in the 2200s, I had a fleet that could crush any other local race's fleet into dust. Someone started a war with me, I beat his fleet down in less than 5 turns, then I sent a massive force of ground troops (my best guess was I outnumbered the city's defenders 40 to 10) and I was slaughtered. I don't think I killed more than 2, but lost every attacker I had. This was with both their soldiers and my soldiers were at the same level. I don't play that mod for that reason and would stop playing this mod if something like that happened here.
Like you said though, in the end I think this is the best mod for Civ IV, and I like it better than my previous all time favorite mod (Civ III Rise and Fall of the Roman Empire).