why no Level 2 support for PMDG MD-11 as PMDG 737 NGX?
You need to understand what "Level 2" means:
it's not that GSX supports a Level 2 airplane better than a Level 1 airplane: they BOTH works absolutely fine, Level 2 simply means that airplane has implemented additional stuff like visible air starters, gpu, wheel chocks, etc. which can be an hindrance to Pushback and GSX recognize them too. The PMDG 747 doesn't have any of that features, which is why it's a Level 1 airplane.
Even Level 0 means a perfectly supported and working airplane, the only meaning of Level 0, is that it doesn't use any custom doors to be opened with gauges or menus or non-standard keypresses, so all the exit commands are just like default airplanes.