It's not my museum ... but I hate to see any artifact dying of neglect.
The problem with a ground level mount will be the accumulation of water and surface rust along the bottom edges. The paint will flake and then serious rust will form. Any components that were in good condition (which of course the Dutch tankers can testify) will deteriorate rapidly. Not only do the grass clippings and mower scuffs harm the paint, but snow and ice drifts 3 or 4 months of the year.
No doubt the current management has bigger problems, it is important for them to know that artifacts that are readily available one decade are suddenly quite scarce in only a few generations. (How much effort has been invested just in Sherman rebuilds in the last decade?) People tend to abuse military exhibits as a matter of course; would a Dutch gallery treat an Old Masters painting the same way?