For the audio we can reinitialise if we have adjusted ASIO properties, and I just discovered it now works when changing buffer sizes, and it’s very handy. (don’t know which version it was fixed though).
I quite often find myself having to restart Renoise because I forget to switch on my MIDI controllers beforehand. Is it possible to implement something similar for MIDI?
Of course it’s no biggie, I can just imagine myself wasting precious seconds before a gig! 
I believe this is a limitation of Windows MIDI drivers implementation: on MacOS, for example, you wouldn’t need to restart Renoise in order to plug in your controller
Fair enough! Do you think this applies to W7 too? I know they changed the way audio was prioritised (or something like that).
I don’t know. I saw on your signature that you are using W7 so I think that this limitation still remains in it.
I think its only the case for MIDI over USB.
Its kind of logical that windows don’t know on forehand you’re having a MIDI device connected over an USB port later, so the MIDI interface is not “mounted”. But it might be possible to re-read this device list in Renoise somehow.
Anyway a useful feature since I’m ALWAYS switching on my BCR (USB-MIDI) TOO LATE! Meaning saving restart loading.