Bluetooth controllers are supported. I just checked it right now with a Mocute 050 playing Asphalt Xtreme and it worked properly. You also can control the system with a bluetooth gamepad as a hardware keyboard. Maybe you didn't configure/connect your gamepad properly.
It may sound stupid but according to the industry standard isn't OTG is a feature resident with a USB device?
Say one can buy a USB flash drive with or without OTG. In fact one can buy a OTG USB adaptor to link a phone with a USD device without OTG. That is what I have been doing all the time!
I believe OTG is just like normal USB cable but with an extra pin connection. OTG cables/adpators are dirt cheap in Amazon.