PErkies are strange things -- by the time you have enough to spend them freely, you're good enough that you're often more interested in the older rides.
If they could be given away, would it change the play balance? interesting thought...
Here's something that might work -- what if you could buy a ride for a friend, but you had to be there to click the button? Kinda like the "join" box used to be...Would let you share the unused wealth, and would let newer squaddies join in perk plane missions, for example. Since you have to be online to do it, would it prevent many of the abuse scenarios?