The backup storage is my guess is the best bet without changing lock formats.
As a homeowner, I've come to the conclusion that the best thing is to have some kind of backup system that relies on a code or something not requiring a key at least. Doesn't have to be a smartlock per se, but some system that allows you access without any key.
Good locksmiths do a lot more than just get into a locked door. I learned the hard way that they can fix doors that were never really cut right, have access to locks and bolt systems that you can't buy as a general retail consumer, and lots of other things. I always thought of them as a kind of backup until I ran into a problem (long story, not really my fault actually in many ways), and they recut the door and put in a very high quality lock I would have never been able to purchase myself. I was kicking myself for not calling them years earlier.