I’ve not tried the tree height mod (s). As you point out it won’t really help the root issue.
But in your case you should be able to get your specific fields FAR77 compliant with a bit of light scenery editing.
See this post
for a link to a description of how to remove trees. The hardest thing I found was getting a download link for Airport Design Editor for MSFS, which I eventually found on the FSDeveloper.com forums: