For me this would be valuable:
1 - Multiple monitor support with the ability to move the mouse between monitors (similar to the p96 utility would be fine, the ability to move stuff by dragging between screens would be a bonus but I have heard that is not really doable).
2 - Better support for badly written 68k programs that work in 68k or older versions of MOS. I have tried on multiple occasions to find the authors to see if I can get source, no luck. These all work on classic amiga and would be great to use MOS for everything:
a. Checkitout used to work fine prior to MOS 3.16, now it doesn't close because it has some bad code iin it :).
b. AmiBack - worked on older versions of MOS with the occasional crash at the end of backup, now it fails all the time.
On classic Amiga's it occasionally (1 in 10 maybe) will crash but normally it works fine. Restores always work.
c. Twist2 - Works but the buttons are not readable in the forms.
d. Ontheball 1.5 PIM - the button for add and update etc. are all trashed.

I would really like to make MOS my full business system, but I mainly use my 3000's for now...