A while ago, a Halo TC was extremely briefly discussed here. (I would post a link, but there was only 3 posts, none of which seemed really relevant)
When I thought about it then, it didn't seem like a good idea. Not enough ships or systems to start off with.
With the release of Halo 2, and the series of Halo books, My opinions have started to change. In Halo 2 you see alot of different Human Ships, and a few varied covenant ships. In the books even more are described (Covenant stealth ships, Human 'Spooks' Stealth ships, civilian vessels, flyable repair docks stations) Artistic license would need to be used, but I don't think it would be too difficult to come up with ships that fit into the Human or Covenant style.
Weapons are more varied in the books, MAC cannons (of varying sizes and fire rates) Archer missile pods, Longsword fighters, Pelican Dropships, Automated point defence systems, Shiva nuclear warheads. Marine Platoons for boarding, and you could even carry a Squad of Spartans for special missions.
The Covenant would have all there ship based plasma and laser weapons, and some of the bigger ships could have planet destroying weapons (leading to missions)
I have only read the book 'fall of reach' but in it some fantastic fleet battles are described. I feel if done properly, these could be duplicated in Nova, and look fantastic. For missions, you'd start as an Ensign in the Navy, before first contact with the covenant, taking on pirates and rebels, dropping squads of marines to there destinations, there are alot of possibilities which would work. Then you could start fighting the covenant, have to test out new weapons and tactics to beat them.
There are a few more systems described, but most you could fill in. The outer colonies, mainly used for resources, far flung military outposts, the Inner colonies (Reach, Earth etc)
So I was wondering if anyone can see any glaring problems with a Halo TC, and if anyone has any other Ideas they want to throw around.