Re 1: Agree, for this exclusive commands it should select the loop. As for the general record command, I disagree for the moment.
Re 2: will check out the prev issue.
Re 3: I had hoped you wouldn't discover this so quickly
I did notice this already, and unfortunately the fix is not straightforward. Due to
latency compensation when you finish a record the playback loop position jumps forward a bit to compensate for the audio buffering already queued up
in the playback system. The sync logic (without rel sync) is pretty strict and won't trigger since it is past time. The fix would touch a lot of stuff I didn't want to touch just yet.
Re 5: Yeah, I saw this rel sync problem too, but didn't have time to get into it as the logic is a little complex for late night.
Re 6: Do you want prev/next variations of that too?
Re SINGLE BUTTON: As a matter of fact I also updated record_or_overdub last night to do a UNDO ALL on a long press (>1s) but didn't bother to tell you!
Big problem for you is the that the exposed AU command parameters don't have the ability to have press/release logic. I have no idea how you would present them to the plugin host
so that you could actually have a "momentary" logic involved with them, maybe treat them as a control with 2 values, 0 or 1, and if the host can provide you with a momentary logic? However, if you instead use SL's builtin midi bindings and have a controller that can actually send separate press/release events (for instance the FCB1010 in note mode) you can make the midi bindings in SL to do it. In the meantime you can check it out using the GUI's keybindings, if you set a keystroke for it, the long-press logic will work.
Adding some sort of double-click logic into SL would be an interesting feature too, not yet there.