I’ve done some searches on the site, and still can’t figure it out. So here is my suggestions.
I use Renoise for MIDI only sequencing, and a note length (gate time) function would be really handy on midi out. The note length slider for the midi instrument is not enough and the note off is not intuitive either. Let me explain with a simple example : Lots of synthesizers use a legato mode to glide between the notes if both are pressed at the same time, it would be easy to program tracks with the length function instead of trying to put it in two seperate tracks with notes off etc.
Another point, really personnal, would be to be able to disable internal audio, so we would not need to compensate to sync audio and midi for each instruments to work in the lowest possible midi latency.
I do use a 8 port midi interface for my outboard gear, an ‘omni’ input would be nice, 2 ins is great, but I think that an omni would cover even more the multi-port issue…
An easy way (yeah… another slider for the midi instr. setup) to set the defautl MIDI volume would be nice…
Maybe i’m too specific here 
but I like the product and think that the MIDI part would deserve some improvements.
Thumbs up for ReNoise. 