I think you wouldn't have to worry so much about opening your muzzle so much - how far do you have to open your mouth to talk? So long as there was maybe an inch or so of room for the muzzle in there you'd be able to talk fine, I believe. Even if you're restricted by it, you could wear a throat mike with a radio on it, cuz you're going to be muffled by a gasmask anyway. As for a hermetic seal - The hood would make it easier, but depending on the thickness of the fur you may not need one, assuming there are straps and things you can tighten, or perhaps manufacture it as two seperate pieces, one which surrounds the neck for a tight seal, and joins to a piece which plops over the head and seals around it - disadvantages there possibly being it being uncomfortable (but no more so than most gas masks, I guess) and it being more of a pain in the ass to get on... not such a problem if you're using it to infiltrate somewhere you suspect there may be some gaseous hazard, but moreso if you're just giving them to the general public.

I totally agree about the gas mask filter placement. At the end of the muzzle is silly, cuz it'll cause the mask to droop. My own mask (SL) has two filters on either side of the head, right up close to the face. There are only two for pretty symmetry, I guess you'd only really need one. XD