Two major points came to mind
1: Fliegerhorst Deelen, 3 runways (2 1700 meter 1 1300 meter) about 10 kilometers north of Arnhem isn't on the map. Feels like it should be there.
2: the canal running east past 's-Hertogenbosch was only constructed between 2007 and 2014 and thus shouldn't be on the map
*small addition in edit: i can understand some of the westernmost airfields like Schiphol, Ypenburg and Soesterberg not being on the map due to not being a factor. Abandoned by the Luftwaffe and out of the target zone.
Thirdly: while i do like the look and feel of the map it feels way too empty. No farms. No villages, only cities and endless fields and forests. Smaller towns important to the Market Garden or Bulge geography aren't there (not even Oosterbeek, Elst, Grave, Groesbeek and Son). I would understand this being because of technical constraints but i do feel the need to point it out.
For the rest, having a blast in the Tempest