OK from my POV first of all /awe

I hope you pull this off - it would be insane.

Anyway I mainly am wondering what difficulties (or impossibilities) I will face if I play all 25 all the time
Well I think first of all, the pre-25 gearing will be insane. Unless Im missing something obvious, theres an exponential amount of time involved as you increase the number of 5 man groups. To gear them up as a whole I mean.

In order to gear up before raiding you are going to have to gear them up in 5 mans. Unless you do one group of 5 at a time this is obviously going to involve running not just one dungeon instance with all the micro-managing of 5 but five different instances of 5 man management.

If you took the other route of gearing 5 men at a time this is obviously going to take a phenomonal amount of time. I mean, see you in the next expansion

I mean, shit, good luck, I claim to be no expert on this but if you pull it off, you can be the godfather to my children

Its possible Ive missed something obvious but Ill leave that to the experts

EDIT - if Ive read your post correctly, you would like to box the 25 man content