Yeah, I'd imagine that it would work. There are many ways to do liners for the helms. I usually cheat and just use some foam padding in the helm itself.
But I'm tempted to pick up that set too. One of the things I've been wanting to do is make or buy a shoulder-mantle like that, so I can pad my shoulders a little. The collar helps keep the mail off your neck, and the aketons back in the day had a similar collar (this predates wearing a gorget).
I need to see how shipping to the US works there.