From "FCC Rulebook"
Every control operator is bound by the frequency privileges of his or her license, regardless of what class license is held by the station owner.
So, if the visiting ham has a lower license, the owners call can be used, but the visitor still cannot go beyong the privileges of his own license.
A visitor can use their own call at another station, but cannot go beyond their own privileges.
If you visit a station of a lower class licensee, and use the station call, you must sign station call/ your call if you go beyond the station owners privileges.
A lower class operator could operate as a third party with higher class privileges if the owner is at the control point.
But, I guess the question is: Do you want to work DXCC as a station, or as an operator. I think most would feel it is the accomplishment of the individual, like you could go to someones station and work a DXpedition you couldn't work from home, and no one would argue that you didn't make a contact for DXCC. But, a station could also work DXCC. For example a DXpedition with multi-ops, or a contest station with multi-ops. I guess its up to the individual what he wants to do.
73, Duane, WV2B
"Nothing great is ever achieved without enthusiasm."- Ralph Waldo Emerson.
