Just do BIAB in your 20qt bot for ease of mash temp controls, and then sub an ice bath for your IC. Means buying ice, but with only 2.5gallons it should cool in a jiffy. In my experience 2.5-3 gal batches just don't leave me with enough beer. Unless you have the time to brew multiple times a month then 5 gallons is much more worth the effort. Then again, maybe I just drink too much.