You can certainly control the BK7M with an external controller keyboard. I use PCR800. I am extremely happy with the module and what it allows me to do.
The controller can store multiple control maps. I use PCR Editor V2, which is free.
I'm not certain what you mean by having the control maps on the USB stick, but I don't think you could do it that way, other than have them stored as backup to the controller keyboard.
You can find a lot of information concerting this and other questions at:
www.roland-arranger.comDonM