Sorry for the delay. Yes having editing capacity is not dependent on having a regions list. However, not having a list means that every time you delete a 'region' from the timeline, it will be gone for good. With a list, I can have a whole palette of sounds in front of me and pick and choose. I can cut a soundfile into 15 different clips, each of which will automatically show up on the regions list. I can then rename these and delete the clips from the timeline. Then the regions can be used as soundfiles. This is an issue in Reaper, which, incidentally, I can't use to save my life. There are many reasons why I find Reaper unusable and this is perhaps one of the very minor issues.
RE actions and an object-based approach. You understand perfectly what I'm talking about. I was actually thinking of a simpler set-up. These are the things I'm thinking:
1- score action, which can also be applied to audio layers. A case at hand is when each sound can be a single grain imported into a table.
2- generic envelope data. For instance, I can draw an envelope for a pitch parameter. I can then save this envelope as an 'object' and drop it onto another parameter where it is scaled both 'vertically' and 'horizontally'. I think, in this context, it would make sense to introduce envelopes that are region dependent, and specific to each instance of an instrument. So I can have two instances of the same instrument, one with an ascending, and one with a descending glissando, drawn as automations. Would this be a possibility?
3- envelope actions, also applicable to pmask envelopes and the table editor.