Folks lager in stainless corny kegs all the time. I've got a Maibock that's been 2 months in the keg at 35*F just waiting for a spot in the keezer. I've done other lagers this way before with no problems at all.
The one thing to pay close attention to when long-term lagering, whether it be in a corny keg, glass carboy or better bottle is minimizing headspace. If you can't purge it with CO2, what's in the headspace is going to be 21% oxygen. That can lead to oxidation problems if you have too much headspace.
Even if you're not ready to drop the coin to do a full dispensing setup yet, try to get a tank, reg and gas line w/ coupling so you can purge the keg a few times before giving it the long, cold sleep.
Good Temp Control -----> Happy Yeast ------> Tasty Brew