Buffet's number one holding currently is cash. So on a macro basis I'm unsure if he has any overall leverage.
It's one thing to use options... but not in the way OP is proposing IMO. Buying a call is a leveraged kinda way to buy upside. But a synthetic long is just something like 80% financed stock... longterm, if your timing is off... that's a ticket to ruin. Even Berkshire stocks can go down a decent amount, since it's fully invested in stocks... so anything but safe.