The 215 with integrated antennas @ 40ft AGL should work fine. Your warehouse design is really going to be about how you manage the clients. If they are decent and can work at moderate SNR (at/around -75) then that should work fine. If you have stubborn, troublesoom clients, you might want to use higher powered APs (367, 228 with 60deg antenna) to create hotter RF directed at the ground, but you will likely need more APs if you need more RF directed at the ground.
That said, the MOST common deployment is the 2x5 or 3x5 APs with integrated antennas, and if you want to lower them a bit to get them closer to the ground, you can do a pendant mount of the APs from a longer pipe/conduit.