Bad Things will probably happen if you try this.
Say you remove disk0 (sda) and take it home. Now the array is rebuilding disk3 (new sda) from disk1 (sdb). disk1 has a problem, and the rebuild fails. No prob, you say, just put back disk0 as sda. Depending on how your RAID system is set up, it may sees two different generations between the two drives, and go with the newer one - the failed drive. It then stars to overwrite your disk0 from disk1, and you only lose the delta between old and new data at whatever point you realize and stop it. Some systems have safeguards that won't allow this, they require "blank" drives to rebuild. If you want to reuse drives from another system, you have to wipe the first few MB or the whole drive for it to be accepted.
The worst case would be if it sees that there's a matched volume (no generation information) already on disk0 and just picks up where it left off, in which case you have different data on 2 sides of your mirror. You get "silent" corruption if either drive fails. AFAIK no system does this, any time you swap drives a rebuild is forced one way or another.
As you said, it only covers one drive failure, either elective OR unintentional.