Ah, Christmas morning. Finally had some time to take a look at Arkos Tracker 2 on my Ubuntu box.
Not trying to ruin your Christmas here (and I know I can't, so no worries), but I gotta say first impression isn't that great.

I haven't read through this thread, so maybe someone has already given similar feedback, I dunno.
The most important thing for me when tracking is to be able to keep the flow. So I want the application to be customizable to the keys I'm used to working with. Such as SPACE to stop the track playing, and SPACE to toggle record mode, CTRL to start the track, SHIFT+F4 to copy a track etc etc.
While you did include a way to define keys, I still can't define them like I want. CTRL can't be mapped. A single key can't be used for two functions. There's no way to copy a track (without marking all the notes first).
This ruins the flow for me, and I just can't work with that.
It also annoys me that I can only play instruments if cursor is placed in a certain column of the pattern, or I've select the keyboard at the bottom. Instruments should play regardless of where I'm positioned, but especially when editing an instrument.
So that's my wishlist.

I know you probably won't (be able to) change any of that, but I wanted to give the feedback nevertheless.