Engineering already had two other BoP pets Lil' Smoky
and Pet Bombling
.. as an added bonus, they were based on your engineering spec, so Gnomish engineers got Smokey while Goblin engineers got the Bombling. AND you got the schematic by renewing your membership card, so you got to destroy then renew your card several times to get the renewal gift which MIGHT contain the schematic..
Much later they changed the schematics to drops..
Then, Blizz did make them BoU (although of course that was AFTER I had dropped herbalism and leveled engineering TWICE for the pets.. ah well..) so I am hoping they do the same with these soon.. I "hope" that Blizz made them BoP for a little while as a bone to engineers to be the cool kids for a little while, then switch them to BoU.. but I guess we will wait and see..