I would personally love that. Give him some extra features if needed.
New Cataclysm mats required. Because honestly, going back for all those silly mats that he requires is just plain annoying and costs a bunch if bought from the Auction House. If there is ever 2x King's Amber on it...
Anyways, my hunter is a freshly leveled engineer so I have to go back to grind the pattern first, then grind the mats in Outlands, vanilla and Northrend.
We haven't had an update on normal repair bots either
Perhaps a guild achievement could be linked to it: *create x engineering items or x repair bots etc* , gives you some sort of updated Jeeves guild version which allows access to the guild bank and acts as a guild vendor as well. With updated reagents, food etc.
An updated model, name and size would be nice as well.