Playing HL2 As TF2 Engineer Possible?

I was wondering, is it possible to play the HL2 campaign as an engineer or other class from TF2?
I don't think so, but i'll ask it anyway (you never know).
It might be possible with Gmod, since I've seen an engineer mod some time ago, but Gmod gives you all weapons every time you spawn.. unless there's a lua script that removes them offcourse.

I'm gonna take a wild stab at this and say 'not a chance in hell'

Well that's clear. I could try it with gmod though