Thanks for the advice, all. I ended up in the public facility in terminal 1. It was what you'd expect for 6 euros (standing around for use, very hot inside the tiny room, which had no place for even my tiny carry-on
) but ultimately got the job done. All the terminal 2 facility options were not possible - JAL lounge said no facilities/access for arriving passengers, and although there is a public facility it is not accessible to arriving passengers (back outside departure security).
So, I'll definitely avoid flying Delta business to Frankfurt again when it is so much nicer to use the *A arrival facilities. My bad not to check first but now I know better. Congrats, Delta management, you "win" again.
Wish it were otherwise, but you gotta give the love to those who love you back.
FTF