I have done this in other leagues - offer a cash price(which can only be used towards renewel in same league) to whichever owner joining in year X (14) has the best record in year X + 2 (16) -- requires the owner to be in the league 3 years and use the money for year 4 (17)
A pretty solid idea as it requires the new owners to really put some effort into their franchises instead of waiting around for the free season.
If we can't raise enough money for the 4-pack ($90) this is also a good alternative.
Which idea do you prefer? Let me know.