I once mixed an eggshell with a semi-gloss, and it looked somewhat uneven when it was dry, but, it was also cheap paint, it held up great to the abuse of a 4-year-old child. but definitely, oil base wont mix with Latex... Your best bet is to make sure that the paint types used have the same base, gloss wont really matter unless your Chickens are picky
Over budget and behind schedule...
That's how I roll :)