MinGW and why Linux users should care

How much of this just consists of setting some flag fields in the output PE executable?

IIRC at least the NX compatibility and address randomisation are flags. If Microsoft are going to get praise for the improved backwards compatibility, they deserve all the blame for applications that don't get the benefits.

Providing suitable linker flags for MinGW that produce suitably flagged PE executables (perhaps by default) would be nice, but it shouldn't be difficult to do it by hand meanwhile.