I've read the lore guide, but I'm still not sure where you're getting the idea that the Legions are exclusively Colovian. The 1st PGE just says that the 'majority' of Imperial soldiers are Colovians, and Bethesda doesn't distinguish between Nibenese and Colovians in-game. (Of course, in practice, that means that we won't either - unless we create separate sub-races for each, which seems a bit OTT.) It just seems rather pointless to state that the entire Imperial military is Colovian, when this a) doesn't make sense and b) has no in-game effect anyway (they'll all presumably wear the same uniform, so cultural markers such as dress won't apply).
Talking of rice... just had an idea about that, I'll add it to the 'Sub-region' thread.