No doubt you could match the level of the 1/4" jack headset feed to the minijack input on the camera, but finding the right lead would be the easy bit.
The headset feed is designed to drive the headset transducer at a moderate level, which would require (I'm guessing) a volt or two, whereas the camera input is designed for a mic feed, which would be of the order of a few millivolts.
You really can get perfectly good results by putting a lapel-type mic in the headset earpiece - it's not that uncomfortable.