Here's the map to give you an idea:
When they started up, they were using a USGS topo. There had been enough changes to the post that roads were wrong and only the major buildings were shown. After I did my first event there, I created a simple map from lidar contours + road and buildings from open street map. Then I added some land cover data from the National Map (to show wooded versus not). I sent them the map and they liked it, so they've been using it. Connie C is the organizer of the Ft Lev races and she comes to a few PTOC and OK events each year, so she knows what orienteering is about.
I think the audience is fine with the current map. It'd take a lot of field checking to create a legit ISOM map. I think the work out weighs the benefits for their use. To map the entire post would be a load of work.
I don't know if there would be issues with permission to map and use the post for orienteering. It is a bit of a chore to go there if you don't have a military ID. You have to go through a security control that adds a bit of work to every visit.
I've been gradually improving the map from newer air photos. Every time I run there, I find something to add or fix.
I also made a "tiny orienteering map" to ISSOM and gave that to the organizers. They've used it a couple of times.
They do still give you a jersey for attending X events (I think it is 5) and you get a sport bag when you hit 2X.
OK has co-hosted an event there the last 2 or 3 years.
IF permission wasn't a chore, the post would be a nice venue for an event. The forest is pretty good (we used it for the 1981 US Team Trails) and the built up areas would be a good sprint venue.