I like it, except I think 12" range is too good a range for it, that improves a whole lot of stuff for one 65point model. I'd say 3" is sufficient.
I've got problems with it though as it means he can move around and bolster units during the game. While that fits the fluff you've written, I think it would be better if he just gave the benefit to one designated unit.
I really don't think the Engineer needs it though. They weren't worth the points at all in 7th edition, now I think they may actually be a little bit underpriced, either that or our warmachines are underpriced, for the benefit the engineer provides. I've played in about 10 games in 8th edition. I've fielded at least three warmachines in every game, and one engineer per three warmachines. I had a warmachine blow up for the first time this past Saturday night, a mortar. In 7th edition I'd have one blow up every other game at best, and I'd field 3 or 4 warmachines, but with no engineers. The Engineer has made that much of a difference in my games. They just don't need to be made stronger.
I think they need to make them stronger if they aren't manning a warmachine. That way there is a real reason to take the Engineer weapons. If they aren't manning a warmachine, they are a waste of points.