One of many suggestions filed by FPC to MA to the coming Mentor system is that use the Mentor skill/rep as a key - experienced mentors could then be granted access even to Gateway. We'll have to wait and see if this becomes a possibility from a technical standpoint, but it is on FPC's "want" list.
I like the idea of mentors getting rep so that you may have an idea of the mentors "quality", however, grating access to the gateway from this also pose a significant problem as those with higher rep will have easier access to disciples with the resulting problem that mentors who haven't yet earned their enough rep to be granted access, have a much harder time getting new disciples as new disciples are most likely picked up already at the gateway, so there won't be any disciples left and so on and so forth.
In my opinion, as a minimum, you shouldn't be able to become a disciple before arriving at Calypso/*planet, but even then, the relation will have been made between the newbies and experienced mentors at the gateway and it's reasonable to assume that the newbie will chose the person they have already come to know.
In conclusion I'll have to say that either there should be access for no one or for everyone, the later of which of course isn't a good idea.
I would instead suggest a step in between the gateway and Calypso/*planet. This place, be it a space station or whatever, would be accessible to everyone at any time, though I think people should be "banable" under certain conditions, and the newbie would, at the gateway, be explained the purpose of this place and have the option to travel there directly, or to Calypso/*planet to maybe return at a later time.
This place would be the only place to find a mentor or to pick up a disciple, allowing for some order and control.
I think the above sound sensible and I do hope I've been of help.
Best regards.