Renoise is extremely powerful for samples, and it allows to use VST plugins. But in my opinion, it can become much more.
What I would like to see added are
a granular (re-)synthesizer, able to be fed with samples from the sampler section
a modular synth rack with a nice UI for the routing to expand Renoise’s capabilities as a standalone powerhouse
It would be much more likely to happen, if the Renoise team could manage to work with this developer to integrate his instruments:
Although it is possible to just use his VSTs, imagine the possibilities of a tight integration into Renoise. You could send any sample from the Sampler into the granular synth to be further processed, and then record that back into the sampler section to slice it up. Or maybe even feed a live signal from the modular synth into the granular section. Or send the output from the sampler into the modular rack instead of an oscillator, to further shape the signal. It would be insane in the best possible way.
The granular option could be implemented as an effect as well. An example from the VST world would be: http://www.meldaproduction.com/MGranularMB
I’d also love to have a physical modelling synth for strings and other resonators directly inside Renoise.
The reverbs could use a facelift and get more features for more creative reverbs. The new Toraverb 2 from D16 should be the inspiring example here.
Again, one could technically make use of the VST, but having something like this implemented directly into Renoise would allow for much more powerful routings, as well as making it an outstanding sounddesign powerhouse on its own, which is important for Linux users, who don’t have the easy access to all the VSTs.
Aside from that, it would be amazing to have a time-stretching algorithm implemented, to play samples freely at a different pitch without changing their tempo. It should have a formant correction, too.
This is currently implemented in NI Kontakt, the samplers from Ableton Live and Cubase 9. It can make a real difference for sound design and is a modern feature that would make Renoise and Redux even more attractive.