I do the same thing with call options, especially when I know something is a bargain but I don't actually have the cash to buy it at the moment. There is no reason you couln't do the same thing with LEAPs. You would just want to make sure that the LEAPs you were interested in were liquid enough for fair pricing. I recently bought a ton of exchange traded warrants (BULKW) that don't expire until late 2008. I wanted exposure to the sector via an undervalued name and the warrants gave me a ton of leverage to boot.
I am somewhat tempted to liquidate part of a long held equity position (PPD) and maintain the same exposure with less cash via LEAPs, but I haven't decided whether I am comfy with this approach yet (plus the options on this name are expensive).
"All animals are equal, but some animals are more equal than others."
- George Orwell