I find that whenever I play CC the right click menu gives me too much options. More after every single mods i download.

In a four player game of CC when everyone wants to play a different faction every player has access to all other factions.

Is lua capable of limiting one player to items, actors, etc. from one faction only? e.g. a small dialog box in bunker building mode which selects the factions (.rte folders) a player can use?

So far, no. Such is planned though.