Heres my opinion on how the channels should be organized:
I can't really decide whether splitting up the tower feeds would be a good idea or not. It has its pros, especially if you're spotting and want to listen to just arrivals or departures, or if you just have a preference of hearing one over the other. It also has its disadvantages where you can't listen to both at the same time and would have to choose, pretty big inconvenience. It would be amazing if it was possible to actually choose splitting them up or listening to both each time you opened the feed, but I guess thats not possible? In the end, I could go either way, but I would say split them up.
I would say split up departure and approach, although its not that big of a deal since departure is usually kept pretty short and brief. I like the idea of having final approach on its own feed. I would also like a ground feed, if possible.
So basically to sum it up:
Either split up the two tower feeds or don't, tough call
Separate feed for final approach
Separate departure and approach feeds
Add a ground feed
Just my opinion