I read through this thread, and I too immediately thought, “SCRIPTING”! So if anyone great at scripting could help, do so please.
help us escape the traditional western scale!
For now, if desired you can try this solution.
I posted it yesterday I think…as of time of writing(22:41 Greenwich Mean Time 22.1.11 or 1.22.11 if u live in the states) it is the last post in the thread.
If this thread is read later, just look for my post with a link to Tobybear Insbag.
Something that bugged me for months and I found a pretty good solution (4 me anyway).
Hope this helps 
Thnx for the tip Tarek, seems to work!
F%^&*-in X-ellent!! 
Glad to be of service…once I figured it out, never gave me any problems 
Just out of curiosity how would alternative tunings work with external plugins? It would be cool if Renoise could support those, maybe by sending proper MIDI pitchbends (as previously discussed regarding tobybear plugin). Actually, is there a host that supports alternative tunings for external instruments?
dunno how it would work with vsti, I don’t think the protocol handles microtuning, not sure though. I’d want to have this for renoise sample use.
http://www.tobybear.de/p_midibag.html check the microtuner,
in combination with energy-xt, bidule, console.jp or the new vstforx
sweet, might even be better than my solution(how did i miss it? 
) as it says add microtonal capabilities to any vsti!!
just to clarify, what do you mean by, in combination with energy-xt, bidule, console.jp or the new vstforx ?
as you know renoise cant route midi between plugins.
so you need some kind of modular host vst to connect the midi ports of the plugins (microtuner + synth).
- to get a microtuner vst(i) (or even mfx plugs) sending its pitchbend messages to the actual synth.
EDIT:
some dev builded a microtune peermachine for buzz and also implemented this feature into his own plugins.
reaper has some nifty js plugins too. but i think via midi-pitchbend automation you can microtune every synth in a DAW and outside of it.
otherwise iirc a few synth do that already on its own e.g. commercial: absynth / free: oatmeal
future of microtuning in Renoise is looking bright thnx to Dblue: Snippet: Load Scala .Scl Tuning File
he is a bloody wizard!!!