This all boils down to 4 very simple questions. It's not all that complex really.
1. Is there anything you can do in Reaper's item based design, something based on, related to, associated with that particular design having some advantage that can't be done in the others?
No. Nothing.
2. Is there anything you can do in the other designs that is clearly not possible at all and/or extremely klunky in the current item based design?
Yes. Plenty.
3. Do any of the track based designs have a "switch" or an option to revert to something like Reaper's design?
No. See question #1.
The fourth question, the one that's a really huge mystery to me...
4. Given the above 3 questions and their factual answers, that all anyone involved would get is "more good stuff", "better stuff", "easier stuff", and not lose anything they currently have at all ... why in the world would anyone not want it, and/or actually - ? prefer ? - having less functionality?
Beats the living heck out of me.
It's twilight zone material.