First a simple question... could you make walls a little stromger or faster to build? Even concrete wall seems pretty useless now. And then a more serious suggestion... You said that players will be able to switch between ConYard and Dozer, but I think you could make the subfactions use the dozer system and original GDI and Nod use ConYards. I'd like that but you can do your mod the way you want to, but think about it.
PS. A small detail: It's Nod, not NOD. Sorry for being scrupulous (is that right word? just checked from dictionary) but that might bother some nerds when reading unit descriptions.