You could make some quick disconnects in the lines, and be able to switch back and forth easily. I'm probably going to do this for a friend soon and figured it would cost around $40 in fittings.
Here's what I planned on using-
One set of corny keg disconnects with barbed fittings ($18)
Three 1/4" npt to barb fittings to match your gas line ($1.50 each)
Three of the same to match your beer line ($1.50 each)
4 male type D quick change couplers (10 pack for $2.50)
2 female type D quick change couplers ($3 each)
Just install the female fittings in the ends of the gas in and beverage out lines. Make some short lines that go from the sanke coupler to two male fittings, and another set that go from the corny disconnect to the other two male fittings. Switching from corny to commercial kegs and back would take seconds this way.
If you're not going to switch back and forth often, I'd just use the MFL tailpieces like jaobrien6 mentioned.