As I've stated before, I absolutely love practical designs in the logic section. There's only so many airlocks you need. That being said, despite the slight reduction in efficiency it would offer, I think a simple logic clock would be better, as well as having it be self powered. The advantage of self powered docked technology can not be understated, power is a very valuable resource to use from the main ship; it either has to come from docked generators or block power on larger ships. Neither of which are paticularly efficient, but you can get amazingly efficient power on things like this, and things quite a bit larger.