Bits of this thread is going into areas I don't know about, so I'll just answer the original question. Well, to start, a major part of my own personal SF writing has been of symbiotic relationships between a certain race, and members of various others, including human. (I did this before I'd even heard of SG-1) So, I have had some experience of considering this. Well, with the Tok'ra, having only seen 'In the Line of Duty', I would consider it. If the bond is volantry, there's got to be a little leinence between the freedom of Goa'uld (Tok'ra, that is) and host. That is to say, the Goa'uld wouldn't need to 'listen in' on whatever the host says or thinks, and vice-versa. As for using the powers of the Goa'uld, that would be interesting, even with the glowing eyes, which is pretty freaky in someone who looks in every other way human. For example, in my own writing, the creature is in tune with it's host in such a way that it protects him/her from attack or harm. However, the cost of this is that the host involontarily loses control over their body.
Very interesting concept, although from what I know, surly it could be a case of 'once a Goa'uld, always a Goa'uld'? A change of name doesn't nesscesarily alter the species.