I think a clarinet would be welcome enough - provided the player was at ease in switchingh between D G and A and so forth. Irish music has always been good at accepting new instruments, starting with the banjo and more recently the bouzouki. I've heard a didgeridoo used as a drone instrument very effectively.

I was in a session recently and there was a fella with some kind of electronic clarinet, which he'd set up so it played comfortably in the right keys, and it was a great sound. Sort of Irish Klezmer.