There's no way the BBC isnt the most awesome resource.
My plan would be:
a. lower cost voluntary fee for users who don't have a telly but do feel love for the bbc/output. Like a 'friends of' fee, perhaps with some access rewards or involvement in internal decisions.
b. A 'would you like to buy the team a coffee' type small payment on iplayer. Voluntary but giving the user a chance to occasionally give monetary Thanks.
c. Some crowd-funded production targets eg 'ab fab summer special' etc
d. A radio-fan voluntary licence club with open events and forums for payers. Low cost, but allows a monetary 'Thanks' for payment.
e. Monetising playlister platform for overseas audiences and asking for cross-payments for signposted content.
I don't have tv and don't pay licence but would pay a 'no tv' enthusiasts or radio fan licence for 1/3 to 1/2 the cost if it were available and badged as such (and stopped the unstoppable letters and 'investigations' that must waste a LOT of money.
As far as I know there is no mechanism for additional voluntary payments to the bbc which is a shame.