ooh, i see what your saying. Yea, there are map optimizers like jaako said. you could also try to use small filesize models and use models that are similar to what you want. i kno....map filesizes suck, lol
Oh! i have tried this yet, but if you place a lot of neutral creeps somewhere, place em with a trigger. it would take awhile, but i bet that would save filesize. i havent tried it yet, but it may work