Thanks for the suggestion. However, partner flights typically earn 0.5 EQM. So it's hard to meet EQM with partner flights.
Anyway, back to my original question: is there a way to use SWU and/or to keep the good seats in economy while earning miles on EY?
I remember when I flew CX back in the days I was able to credit miles to my CX account (since their discount economy will earn no credit on AA) while entering CX first class lounge by swiping my exp card at the lounge entrance. OW partners seem okay with that.
However EY might be a bit complicated as it doesn't belong to OW. YMMV.