A shame you are thinking of demolishing them, they are a good kit that deserves an effort of time and patience to create a great end game.
Okay, I've given this some more thought, and here's what I propose to do.
It is too late for extensive painting, as you said, but the "bare wood" look isn't at all bad on them. So I'll look into pinstriping, and I generally need to do some detailing.
The passenger coach gets passengers (duh) and maybe then I'll glue the roof on. I left it loose but this is impractical: it comes off too easily and is difficult to put on correctly.
For the mail coach, the main thing is to stop the doors from swinging back and forth as they are doing now. I still want them to open, because I want an interior that's fit for sorting the mail during the journey. This is something that happened on the majority of Dutch intercommunal tramways.
Next thing, I'll create a loco that visually fits the coaches. I think I may be able to use parts of my Otto for this.
Finally, give this set a more prototypical type of couplers, which also means they will truly remain a set as I don't plan on replacing the LGB couplers on other stock.
I think that with these measures I'll have something that belongs on my tramway. Thank you for defending my coaches.