The current coverage of NAVAIDs makes it impossible to fly some procedures (you don’t receive a VOR bearing above the MEA, you don’t receive the ILS signal at the FAP, etc).
A great improvement to this aspect of the sim would include:
Realistic NAVAID coverage
Realistic behaviour (cone of confusion, VOR errors, NDB errors and lack of precision, false LOCs, false G/S)
The ILS localizer has a limited range, far less than many published instrument approach charts require. The SDK allows realistic distances but when compiled they are chopped off and all ranges are the same.
Which is an issue 
sure. but only if it can be toggled on or off. Give people the choice. like with Turblence
Yeah I noticed some of the approaches aren’t available in the FMS. The system is outdated. I would love to be that guy to update the system for the US.