nop, sorry.
All I can do is cancel, requeue for every mission ... and maybe have the same mentor mission again!
I've tried it several times but had to resign accepting it in the end most of the times.
So you're right, I know it's going to be a mentor one, but I can't avoid mentor missions if I want to play (yesterday evening with a friend: we only played mentor missions ... sometimes with antags 207 by the way!)
And again, the problem is not helping new players (since the game can't do it itself!) but having them when you try to get a high score for a blueprint or else.
Personally, I would turn off antags and mentor for daily rewards, then put mentor back on (and maybe antags, if I play with friends in an organized team)