What did Severus want to do as an alternative career? He actually declared his secret passion to Draco after dragging the young student into the bathroom.

(Notice how I avoided the pron there.)
The Potions Master wanted to be a Master Thespian! Here is a version of the later bathroom scene in HPB between Draco and Snape (where I obviously copied the figures - or tried to). They were both ACTING! Genius!
Of course, Snape's greatest bit of ACTING! took place in the Shrieking Shack in DH. ;-)
ArtPad for fussiness over skill.