I think he would still be Goa'uld rather than Tok'ra since the actions of the symbiote are enlightened self-interest rather than philosophical belief in the freedom of the host. He gets a powerful, er, father-in-law by allowing his host to time share rather than subjugating him entirely. Neither the symbiote nor Methos have any problem with other symbiotes subjugating other hosts.

My take on Joe is that he's quite content with his mortality, especially if the alternative is to give up even an ounce of his self-will. He and Jack O'Neill would probably agree perfectly.

It would be clear to the SGC that the host does have some autonomy, but they'd probably see him as being traitorous rather than a demonstration that the symbiote is good.

In this version of the crossover universe, the SGC takes the big view and Methos takes the individual one. SGC wants to destroy the goa'uld as a race, Methos wants to deal with every single symbiote (Goa'uld or Tok'ra) on an individual basis.