1. There's a Map Editor. Try TWC in their download section. I don't know how effective it is yet since I just got it myself and haven't tried making anything with it. However, CA did say it's already good enough that they don't need to release an official campaign map maker.

2. Yes. In every model weapons are named as "primary weapon" or "secondary weapon". The engine look for these names to show the weapon in-game.

3. Yes. I don't remember the exact file names (not at home puter atm) but they're in the Data/UI folder.

4. I don't think so. I haven't seen any mod that could have less than 10 factions from the start without the "Faction destroyed" message.

5. Yes. It requires you to edit the model in 3DSMax. Either you unfold the UVW or just swap the shield with one that's not quartered.