I'm not sure if you saw my recent post to list looking for exactly such a plugin! I'd be pretty intrested in something similar to that.. And I've done a little reading around: bbcut (as suggested by Dave Phillips) is an awesome library for slicing & repeating stuttering etc, its written for SC & CSound, and there are standalone versions too.

Using CsLadspa I think it would be trivial enough to provide a LADSPA interface to a csound bbcut file.
This would however not provide the "tempo sync" that you're after. Of course one could create a standard LADSPA control input port, and label it "BPM", and hope that the host knows what to send it. Or that the user does. Obviously not an idea situation.

Although LV2 could support BPM / subdivision info, that would need a extension for that to be written, AFAIK there isn't one available yet. (I'm aware LV2 is ruled out by Renoise anyway..)

I'm not a great supporter of native VST's, my experience using EnergyXT 2.5 & all the linux vsts I could get my hands on wasn't particularly sparkely: some crashes, XT froze a bit, random latencies... :(

What I've been doing recently is wrapping LADSPA plugins with custom UI's. Its not that much work, and I've got a set of default widgets like frequency graphs & ADSR like done which make the work go quite a bit faster. I would be willing to write a "custom" UI for a LADSPA plugin that does this sort of thing :)

I'll be keeping an eye on this, -Harry