You may want to take a page from the Citibank "CitiMiles" program. This program requires that you spend $15 to earn one mile but when you redeem the miles, a mile is a mile. As an example, Tampa, Fl to Bahamas is charged around 500 miles. Since the bank buys the ticket, you have some choice of airlines and can thereby earn FF miles. No blackouts but Saturday night stay is required. No expiry but must originate in USA

I find this program to be idealy suited for out of the way, not too distant (read expensive) destinations.