I've been doing some tag edits as time permits.
Realizing one of our problems is the sheer number of tags, I hate to say it, but I've been thinking of adding a 'mechanisms' tag. We have lots of questions about various mechanical devices on and around spacecraft, but I didn't see an applicable tag.
For instance, this question ISS Structural Integrity could really use another tag besides 'iss', and 'mechanisms' seems to fit the bill.
Edit 2: Looks like 'avionics' exists, yay.