Bought the house, bought all the upgrades except the enchanting bench (my character doesn't use enchanting)

Went there, the pedestal the mannequin usually is sits right in the corner as it should, but no mannequin. Is there any way I can make it appear normally, or do I have to use consol commands?

He's https://www.youtube.com/watch?v=iRZ2Sh5-XuM. He may appear again eventually. Try leaving the city and waiting a few days.

Well, I purchased the house a while ago and it wasn't there.

I've had it long enough to fill the empty room like crazy with random misc. valuables to make a 'treasure room'

Never appeared, hasn't yet. Should I enter, leave the city, wait a few days, come back, then keep trying until it spawns?

If you've been visiting the house the entire time it'll reset the respawn counter. Leave for a while and wait a few days(I don't know the exact number)

If it did not appear when you moved in it is not going to appear ever. Perhaps you should try buying all the upgrades for the house? Take out what you have already put in your spare room though. The upgrade you skipped is to furnish the enchanting area, it is more than just an enchanting table.