I’m presuming it’ll be D fully, as much as I dislike the idea of the MD-11 and B764 being able to be there (Nothing against them, love them both but not realistic). The B763 was a regular visitor in the 2000s conducting charter flights to the Caribbean, Africa and Asia from mainly Lauda but a few others too, Austrian and KLM too. The airport can take A330’s, only one though famously, which would be a cool bonus maybe pass aircraft if the devs have any way of forcibly making a single contract a D class.
I wouldn’t know how stopping certain D class aircraft would work as per CJ’s post above, maybe they could be sold or maybe a one time option to switch them if that’s within the devs power.