What would you do if the forum had a subscription fee (to post classifieds, etc)?

i) I don't think VB should be bound by the views expressed in the poll: informed, but not bound

That, begets this...

vii) I quite like VB's solution as proposed above, though not sure I'd necessarily want the fact someone's donated to be too obvious

And the donor status would not be obvious, it would be discoverable. It would be on the profile page, but not beside every mention of the name.