Sorry, I meant 255. I wanted to point out that there's a conversion necessary from 2 MIDI messages to 1 DMX channel, since MIDI messages (at least Note msg) have only value 0..127.
Ok, so bluetooth-wise that doesn't seem to be that easy. The Wifi solution is too expensive, as well as the ethernet solution, because I would have to have a separate Wifi router for linking the networks.
Maybe the Arduino is not a good choice for that. I will have to look at a raspberry pi, which has more capabilities for just a few bucks more.