Even with all these I cant imagine that poster plastic not being able to be painted. Even if you just sand and scratch it it should accept that awesome spray paint.
I'm definitely gonna give it a try since my original plan was to go BB to make me feel safer having Discus for the first time, but hey, if I don't like how it looks I can always add PFS. My husband after hearing me go on and on about the issue said "if you could do any substrate you wanted with this tank what would your first choice be?" I answered "SAND".
Good that you are sticking to it. I really think that bottom line you will be fine with either way you choose. THe ammount of work you have put into researching and putting it all together shows you will do what you need to to keep these tanks running.