I am sure there are a number of safety and engineering considerations, as well as future integration and flexibility to consider, but I can't think of any so far.
When I think of an airlock, I think of something with two doors - one at each end. I don't understand how this works - To deploy, does it open like a clam shell, or does it just open the one air-lock that also mates with the ISS, and deploy from there? It seems that it also requires the ISS's Canadarm 2 to grab hold and move it away from the ISS. I can speculate, but I am wondering what the real reason is. Is it too dangerous to just push them out with springs?
Since everything is in orbit, the usual concept of "away from the spacecraft" is a little more tricky. Does this make it possible to change the direction of the deployment-nudge to something better suited to avoid future collisions?