From my side as a big fan of TC when were working on PC 5 years ago, is the max functionality of FM on Mac. But later I sticked with 3 main things:
- convenience and speed
- archive browsing (the thing than no archive app on mac can do). So, thats very important feature that can substitute archive programs
- fast any file viewer (text/picture/video) on the other pane.
My proposal to monisate the project is simple: get most useful features out of free version (cause most of them are working, as mentioned earlier), and continue development of paying version.
If you know the amount of free users, you can calculate how many of them will transfer to payed version for better and unique on the market functionality.