WWARA does have a monitoring program. We periodically check to see that coordinated repeaters are "still on the air". This is a semi-automated process (computer-controlled radio interrogator/logger) conducted on an approximately semi-annual basis, and it does a good job of finding "paper repeaters". That is one thing we are very sensitive to, a "repeater on paper, but not on the air". At one time in the distant past, there were lots of these. Some were machines that the owner hadn't actually built yet, and wanted to "hold his spot" until then. In order to maintain a coordination, a repeater has to actually function. WWARA policy is that a repeater that is off-air for more than 6-months is in danger of loosing it's coordination.
As for setting a minimum level of activity, I don't really see how that's our business. I get your idea that in a perfect world the repeaters that are on the air would be constantly active, such that you'd have to stand in line to use them. That might describe the repeater world of the 1970's or 1980's, but not today. Why? Cell phones.
In the 1980's Hams used repeaters to chat, because we could. There wasn't another option available. You could certainly call someone up on the phone, but that meant you were tethered to a wire. The idea of carrying an HT on your belt with which you could actually make a phone call (while walking or driving around!) was a very big deal. Many repeaters charged a monthly (typically $25) fee for autopatch use, which funded the entire project. I used to use the autopatch on the Scottsdale repeater to call my wife and let her know I was heading home. From my vehicle! In motion! This was almost science fiction to the lay person.
Now everyone has a cell phone. Where we used to chat on repeaters, now we do that on Verizon. If you want to understand why our repeaters get so little use, that is the salient fact. It's not 1980 any more.
I don't understand your concept of "Enhanced Coordination". According to Part 97, a repeater is either "recommended" by us, or it is not. Putting a designation on our frequency list that "picks favorites" seems like a "teacher's pet", and just as dangerous. How does a coordination body focus on coordination criteria and maintain an objective detachment while at the same time designating "teacher's pets"? Just because a particular repeater is busy all the time doesn't mean it is any more or less valuable to the Amateur community than another. Drumming up business for repeaters is not our brief.
I would suggest, extending your logic, if any group would get priority use of our repeater spectrum, it should be the ARES/ACS/ACES folks. When the phones/internet go down, that is exactly the time those repeaters will be invaluable. If those public service repeaters are replaced by the "constant idle chit-chat" machines, then they may not be well placed, or available, for the few times when they can be of most benefit to the general public at large.
Ultimately, our mission is to provide a service to the general
public. That is why we have the use of a generous portion of the "publicly owned" radio
spectrum. So, if there is a priority to be set, it could as easily be
"service to the general public" rather than "service to the Amateur
community". I know the Emergency Management Director here in Pacific
County gets a warm-fuzzy feeling every time he talks about being able to
contact Camp Murray over Ham Radio when nothing else is working.
Disclaimer: I should point out that I have been active in ARES/RACES as a county Emergency Volunteer Worker for over 38 years. I built the BeachNet
repeater system (with lots of help) specifically for disaster relief communications in the "lower left corner" of the state. It has been successfully used in this regard several times. To mention only two (Nisqually earthquake in 2001 and major storm damage in 2007-8) when commercial communications went down for the count and we needed a way to connect with the State, each time it worked as intended. Now, as far as I'm concerned, those isolated but recurrent episodes are enough to justify the expense of maintaining the network and holding onto the frequencies. But, then, I'm biased. Is the system busy? Well, with a population of about 2% of Puget Sound, in an area about half the size, spread all over the Coast Range, it's about as you'd expect.
So, if we are going to set priorities for the use of the spectrum, I think we are getting very near a slippery slope. Each repeater owner has his/her own priorities and reasons for putting up a machine or machines. Those reasons may not make sense or resonate with others, and they don't have to. If someone has the license, and wants to strap on the expense and effort to put up a repeater, then it's our job to try to minimize interference. Making any sort of judgement call as to the relative merit of one project over another is not something we are equipped to properly address.
I think WWARA has done, and is doing, a good job of "fitting as many repeaters into the available spectrum" as any coordination body. This is an activity that is always spectrum-limited, particularly on the 2-meter band. There are historical reasons for this being the most popular band for repeater-based communications. It is interesting to me that, while we have a significant pressure to provide spectrum space for repeaters on 2-meters, there are open frequencies available on several other bands. I often mention to frustrated would-be repeater operators that they would have lots of possible places to go on 6-meters or the 220-band, with propagation as good or better. No interest.
I'm not trying to shoot you down. I'm just pointing out that this ground has been trodden previously.
The problem before us is to look for a way to transition in an orderly manner, from the present Band Plan to one where 20-kHz analog FM machines can continue to exist as long as their operators are willing to maintain them, while providing a way to efficiently accommodate narrow-band repeaters, possibly using a variety of digital modulation schemes, on frequency assignments that the equipment is actually able to tune to, and over time, promote an orderly shift from a predominance of the former to the latter, with the ultimate goal being an all digital landscape with as efficient a usage of spectrum as practicable.