I was talking to a guildie the other day & the topic of mount rentals came up again. This is how I think it could be a win/win for GF.
1. Mount Rental Vouchers would allow you to bind one of your mounts to a voucher. This means that the mount cannot be summoned without the attached voucher. When the voucher disappears or gets destroyed, the mount is freed from the voucher binding and is summonable by the player like normal.
2. Mount Rental Vouchers and costs
2a. 2 hour MRV, cost: 1 dia or 10 phirius tokens
2b. 12 hour MRV, cost: 3 dia or 60 phirius tokens
2c. 24 hour MRV, cost: 5 dia or 100 phirius tokens
This would allow you to put up a voucher in AH, pass on to a friend, negotiate via mail, etc... The most important thing is that the voucher is NOT the mount, but a way to summon the mount. When the voucher is destroyed ( timeout or thrown away ) then the link is broken, the mount is unsummoned and the mount goes back to being a normal mount for the original owner.
So if you have a stable & want to help friends out, you can buy vouchers w/ dias or tokens. ( & if you want to make some gold, rent them out )