I think it depends upon what part of the plan you are talking.
In terms of the "new" low-fare operation that will debute sometime in winter, I don't think DL will need pilots approval. For example, if DL takes a 757 and strips it down to one-class, that really has no impact on the pilots as the payscale stays the same. Of course, Leo might want to renegotiate payscales for the "new" low-fare operation...but I don't think it will happen.
If the DLX 732's return to mainline service, I believe they have the same payscale as the 733's (correct me if I'm wrong).
In terms of a codeshare alliance, that does require pilot approval and I think Leo's going to have to make some BIG concessions to get it through.
Otherwise, DL seems to be making capacity reductions here and there....trimming mainline down in many markets. Sad to see a route like ABQ-SLC lose its last mainline flight, but DL doesn't really have many other options.
I wonder if DL will attempt to "de-peak" ATL similar to what AA is doing at DFW? In April 2001, I remember there were plans to smooth out the ATL operations, but I'm not sure whatever really came of it. ATL still seems to have the standard bank structure...though the banks almost run together.