I don't know why are you limitling the Starcraft universe to just the ground battles if each race has its share on Caps and fighters.
Ok basicly we only know on cap and one fighter for each race. With SC2 there will be some modifications to some of these classes that could make nice sub classes. At least to the terran ships.
I mean what to we got (SC1+2)
I have put SC2 ships in [ ] because the final stats/abilitys are not know.
Terrans/Humans
- Wraith Fighter
- Valkyrie Missile Frigate (could be a second fighter)
- Dropship
- Science Vessel (if you could get its special abilitys to work it could become a valubal unit)
- Behemoth class battle cruiser (this is the old SC1 version that can be upgraded with a Yamato cannon)
[[ - Hercules- and Minotaur-class battlecruisers ]] (these are the SC2 design that are replaceing the Behemoth class. They come in three flavors, normal, plasma-torpedos and Yamato cannon)
[[ - Viking ]] (not sure if that should be listed as fighter also but it could be fun if you get the transformation working and then you set your fighter as a turret on your capships hull ^_^ )
Protoss
- Shuttle
- Probe
- Arbiter (His special abilitys could be interesting if you get them working)
- Scout (light fighter)
- Corsair (heavy fighter)
[[ Phoenix ]]
[[ Warp Ray ]]
[[ Mothership ]]
- Carrier (two versions exist. The SC2 version could be seen as the modern, lighter carrier while the SC1 carriers are discribed as "...heavily armed "super carriers" exist, most famously the Gantrithor..."
Zerg
- Overlord (aka transport, command center)
- Mutalisk (medium flyer)
- Scourge (light kamikaze, when well done these things will realy become a pain in the players ass. Maybe they could be some kind of missile for the Overlords)
- Guardian (I think I have at least seen this one in a cutscene in space so they also be able to operate in space)
- Devourer (again a very specialised unit that would only make sence if you get the abilitys to work)
I don't have much info an what Zerg units are comming with SC2 so their list is a bit shorter but hey. Zergs are working in numbers you don't need many different units, just throw a ****load of them at the player...except you want to player to play as a Zerg ^_^
So to the WH40k/Battlefleed mod...beside I have never seen a finished one.
Or make the greebles as textures and normal maps.
That would work only to an extend. At least the imperial ships are basicly flying cathedrals. The sheer number of details they have mean that you have to reduce them a lot and that can't be made up just by textures...well depending on what quality you are looking for. Also remember that these ships are massive. It is a modeling nightmare.
There is a guy at Sci-fi-meshes.com who is working on an Imperial ship. Just take a look at these any you will see.