I'm probably wrong but I feel like NATCA should be pushing for facility upgrades to be based off of traffic count and/or passengers. The FAA gets a lot of it's funding from the
Airport & Airway Trust Fund which I believe nearly the entire Air Traffic budget was paid for by it. Many airports have increased traffic count yet decreased operations due to larger aircraft being used. More rules/phraseology has been added to the workload since the level system was implemented and I doubt it's been revisited.
Before anyone says VFR towers would get screwed, the AATF is funded by fuel tax as well as passenger fees so they every VFR pilot is contributing as well.