Would about a new Meta Device for recording the incoming audio? I know this can currently be done with external plug-ins but there are a few tweaks to make this particularly useful for Renoise.
Obviously the ability to use more than one, tied to an Instrument slot, so you can record multiple input channels at once.
When recording over a looped section it would create a new slot within the Instrument for each time it loops around and subsequent recordings go into a new slot, rather than one long, continuous file.
A check box to Arm on Looped Section so you can play an intro and then start recording takes once you get to the right part of the song.
Preferably it would be recorded as a single file with movable markers so you can adjust for slight timing errors, at a minimum “handles” would be good (extra seconds either side of active part of sample, commonly used when injecting for video editing.) - This is probably the hardest part but may be possible with scripting as it allows some copy and pasting between samples but it would also be a lot slower if they are actually separate files being manipulated, rather than markers changing position and then you Exporting final decision as a normal sample.