Harvey is an old timer merc. He joined at a very impressionable age, full of Uncle Rob's stories about The War which always started with "So there was this girl..." . While Harvey did cut a bit of a swath through the ladies when he was younger, obviously it didn't quite work out that way for him. Harvey's been in so long he knows alot of people. Although he's an accountant, he's also *very* good at arranging for his squad to be, uhm, well equipped. Harvey is a tank driver, not a mechanic. Ironically enough, the mecha will have some basic mechanics for self test/self maintenance.
The link he has with his tank/mech is due to some experimental tech which was decided to be not worth the effort of continuing the project, but of course cannot be removed now that it's in. Once the link is established, Harvey is no longer there... Hivemind is... And Harvey (being no longer there) cannot get himself out of the collective, somebody else must initiate his release... (Please be VERY careful to get Harvey loose ****before**** turning off the mecha. Otherwise things get **very** unpleasant.)