I would just ask very nicely at check-in, and again at the gate. Besides DL, I've only ever flown on WN, LH, and LX. WN only has Y, and first class was sold out on both LH and Swiss. For those 2 though, I asked at check-in and again at the gate and I'm pretty certain had space been available, they would have put me up front.

DL is pretty notorious for putting OAL nonrevs in F. Not so sure about NW.

It can't hurt to ask..