Mp3 is a licensed format, this is afaik why you can’t mp3 directly with Renoise. I recommend LAME + RazorLame-frontend for quick mp3:ing though.
About your second question, what would you use such high samplerates for? (Personally I only make music with Renoise and am completely satisfied with 44.1 khz as this is the samplerate my tracks will be presentated in anyway). I don’t know about how well VST’s and VSTI’s handle these samplerates either, the serious/commercial plugin will probably fix this but the others…
You forget one thing:Renoise is a German product and Taktik’s company operates under German law. Germany is highly strict when it comes to obeying the law in this matter and the fines (and prison terms) are
not the kinds of troubles you would even wish your enemy to collect if German authorities are dropping those on your neck. I would specially not mess with Fraunhofer if i would be a German myself.
I fully understand his situation that he is rather safe than sorry.
The idea sounds nice but is on the edge, though it is Taktik’s party.