Moving main service breaker panel lower on wall exposes feeder wires non-sheathed

I am replacing my main breaker panel and want to add a cutoff breaker inline before the new panel. To do so I will need to lower the new panel about a foot. The problem is that the sheathing on the 14/3 feeder wiring does not extend down the wires into the panel. It has been stripped off and stops right at the bottom of the cable clamps. The wire above the new lower main panel would have the hot, neutral and ground wires exposed above the top of the panel where the sheathing stops. Is it acceptable to run these wires inside stubs of conduit coming out of the top of the new main panel? I'd rather not have to wire nut new Romex onto all the runs above main panel and have them secured in junction boxes.