Why didn't you get a car with leather?
Yeah I'm confused why you wouldn't get leather to begin with if you hate cloth...
Having it done custom is definitely your best route, though you do realize it's completely money down the drain in terms of the fact it adds zero value to your car when you sell it. I think financially you'd be better off just selling your car and buying one with leather (i.e. a WRX Limited). Though again I don't understand why you didn't just get one of these to begin with...
These numbers aren't exact but just used for comparison purposes:
Your current value = $25,000
Custom leather seats cost = $2,500
Value after seats still = $25,000
Cash out of pocket = $2,500
Sell your WRX = $25,000
Buy a WRX Limited = $27,500
Value after purchase = $27,500
Cash out of pocket = $2,500
So you'll end up with a car worth more but with the same amount of cash out of pocket.