Well in simplest terms, someone has to come up with the payoff before a leased vehicle can be traded. You don't own it so you can't trade it. You are a renter.
Also under terms of your lease you would be facing an early termination penalty.
Best thing to do in my opinion would be to find someone to take over the remainder of your lease, and then, being free of the lease, you can then go to the dealer and either lease or buy what you want. Your lease might sound attractive to someone else--it's not too bad a deal, looks like.
Banks used to allow leases on used vehicles but they have pretty much stopped doing that, so if you want something used, I'd bet you'd have to finance a buy, not a lease. Or you could lease something new. Or you could just run out your current lease and make it all very simple.