Six will unrestrictedly get behind the pro-vegetable campaign. Man cannot live by prehistoric canned food alone.
I'm really fond of the notion of Six trying to recruit him, tbh. If she's going to end up doing her level best to oust Negan, she'll need to put together a cadre of Saviors like Mick, who may not be true-blue Neganistas but can still be bloody terrifying if necessary (and, more importantly, who she'll be able to trust not to start hankering for the good ol' days under Negan). The only reservation I see her having is if she twigs to his association with Ray; she'll not want to do anything that leaves Ray exposed to the Saviors. If she becomes convinced Mick's defection would end with Ray tagging along, she'll shut her trap pronto.
Otherwise? Hell yeah! She can certainly try to sell him on the Saviors. Big-ass guns, minifridges, and non-compulsory vegetables. C'mon, dude.