I imagin wizard regents to be like Merlin, or so many historical "wizards".
Because of their tie to the land, the landed regent and the wizard have a
natural point of cooperation. Neither want to see the land harmed. I think
that wizards play a role (albeit a small one) in the "land's choice" so that
wizards tend to get along with their landed peers. I think any kind of
regent is political. Further I think that running a realm is a full-time
job and leaves no time for other activities. Monarch's like England's
Richard I did a great dis-service to their realm by being away for so long.
While a campaign where the players are off and about to the four corners of
Cerilia sounds like a great and fun campaign, its probably best if the
players were second sons of existing regents, or younger brothers. This
would provide much of the same revenue and safety, while not shorting the
role of regent.

As I have mentioned at other times, I prefer to give player regents more
than they could ever do. I want themt to have the sense of just keeping
their head above water. And certainly not leaving the realm unless it was
more important than the things that were left un-done. I try to have six or
seven story lines all working at once, plus a large number of random events,
all of which have consequences. No event is a catastrophy, but the
cumulative effect of choosing poorly (short sightedly) over several season
could have a catastrophic consequences.

Kenneth Gauck