Hi,
Both breeds would find mixing with your Pekenise no problem if handled correctly, and the same goes for any Peke. However both breeds would find it traumatic to suddenly leave an established home, companion and routine after a year. Collies are notorious for their need to stimulate their minds (not a negative point, just being a real dog!) and if left to their own devices after having company all day will find a way to alleviate the boredom. Be warned it will be an activity that is stimulating and enjoyable, for the dog, not you! Many people don't realise that the GSD can be taught to be almost anything, but nature plays a part too. The most carefully bred litter of GSD's, meant for instance for police work, will almost always throw a very submissive, a sound shy or a nervous pup. If a good sound dog is thrown they are relatively slow to mature and a sensitive dog can be ruined by inappropiate handling. They are intelligent animals.
To minimise any problems the best answer has to be to spend the next year researching the breeds and wait until your housing situation is decided before getting a new dog. New start, new house, new dog you can enjoy properly!?
One more thing to take into consideration, about ten or so years ago the kennel club of Great Britain were lobbied, and considered (but not too hard!!!!), breaking the Border Collie breed into three distinct breeds ; working collie, pet collie and show collie. This must tell you something about the vast range of genetic difference in temperament within the breed. I see the same difference in any working breed including GSDs, check the parents out!!!