I don't know about the computer building the cheapest things first. Playing as English and after I had taken over all of Spain but with no money in the bank and insuficient funds to cover all building/training - the queue seemed to go from my homeland first and then spread outwards and hence could not build or train anything in outlying provices ie. Spain. Even though was cheap buildings & units.

I personally would prefer it if the cost of a building was spread over the construction time. Who would buy all the stone/metal upfront for a fortress that takes twenty years to build??? That way if you were low on cash you could at least get the thing started and finish it when you had more money. Thay way if the enemy invaded you might have to try to keep him out of a half finished castle which would make sieges more interesting - for me at least.

Also imo, a list of breakdown on upkeep, capital and training expenditure would be good. When low on cash I routinely go through every province and cancel all building/training and start queue from scratch again but its hard to keep track of when you hold a lot of provinces.