Related to OP question, I'm in the likely somewhat unusual position to be both DL diamond and skyteam e+ with another airline. But I have a large pool of DL miles for which I mostly see value in US domestic Y. However, I'm wondering is there are ways to book a skymiles Y domestic award on DL metal (to get c+ seating if buying 'main cabin standard' award, but use that other airline ste+ status to access DL's lounges on those same journeys.

Thoughts?