Back in 3rd ed, I played a Bjornaer. In 5th ed, I have mostly played Ex Misc, with a brief experience as a Merinita in an aborted saga, and a few months as a Bjornaer.
CJ wanted to run a different saga for a bit, so me and two other players all said we wanted to play Bjornaer (I wanted to be a dolphin, the guy who usually plays a Flambeau wanted to be a salamander, and one wanted to be a heron just to mess with house Bjornaer). We ended up with a sept/covenant of Bjornaer in the mediterranean, with two other Flambeau with Heron heartbeasts....and a Bonisagus, because one player really,really didn't like Bjornaer and didn't want to play one, so we decided our covenant would hire in a guest researcher. Our purpose was to make sure at least one of the three Heron heartbeast magi survived long enough to become a great mystagogue and take over Clan Ilfetu. We turned up to discover our leader and guardian with a lion heartbeast had been murdered, and proceeded to see off the attackers (although my beautifully designed berserker grog died in the fight). We ran about 20 sessions before our SG got bored, but had a lot of fun exploring the Theban tribunal and travelling to Crintera.
So, single house games can work amazingly, but roleplayers being roleplayers there's always one who will refuse to run with the theme and insist on something else, so I'd recommend allowing in a visiting research magus, or a hired gun martial wizard, or something else to allow a token non-themed one in, or give the person who doesn't like house X a book with cool suggestions for Mythic Companions in. Thinking about it, Transylvania with its insistence that Oppida have at least one Tremere and at least one non-Tremere makes for a perfect compromise.