The problem here is that--- Well, something is ALWAYS broken, and always will be. I've got so far about two-dozen different sites, about half of them are running different types of machine, each with Serial Numbers started with 100 or less, which are constantly breaking in random / different ways.
Here's how this works:
I notice something like the watt/kw/whatever problem I described originally- Clearly, this is Broken, and isn't working right. Great. Now I know. It happens just often enough to Annoy Me, but not often enough that the people who make the equipment care. So, the People who Make The Equipment tell me things like "Well, you know you can only poll our equipment every 10 minutes on obverse full moon, or else it isn't going to work". So, fine, okay, I start polling every 10 minutes on obverse full moon cycles, and some other Dumb Thing pops up with that, so round around it goes again. Eventually I inevitably get the "we haven't seen this before", and then it ends, and it just stays Broken until I roll out metapoints or some other random workaround to get it working.
No matter what, it seems to work for about 143 hours, and then they remote-update the firmware, and some other Damn Thing breaks, since everyone designs everything nowadays to basically require field firmware upgrades every 48 hours, which of course they DO, and then the wheels fall off some different point. "Oh yeah, we forgot to tell you that the current register is now expressed in mA instead of Amps, and the volts have been converted to ergs-per-unit area, because someone thought that was a good idea-- Also, if you don't read it every 10 seconds, the Inverter shuts down the Modbus and won't respond to polls again unless you power cycle the inverter and poll it within 30 seconds. That last thing ACTUALLY IS TRUE.. That was a Huge Pain to work out.
While in principle I completely agree- I do need to know if Something is Broken. But I'm talking largely to Solar Inverters, in quantities of dozens at a time. The sales life of these machines is maybe 2-4 year, and then the manufacturers really don't seem to care about fixing Broken. So it falls on Me and Mango to report data the best I can, so that we can tell our customers when their machines are broken, and if so offer help in fixing them. I've had hours-long with most major domestic inverter manufacturers, and comms is like 80 on their list of things to fix. Or, they say "Well, you have to work with our Integration Partner, and pay them $12,000 for their Magic Box, which converters Modbus/IP to Modbus IP for some reason, and has their own firmware update cycle, and blah blah blah" Once the Next New Machine comes out, the tech support for previous machines instantly dries up, so no one cares about fixing these things any more.
While I appreciate the Meta-pointedness gusto of doing such a thing in a metapoint, I already sink hours and hours into fixing and mapping broken and ill-defined modbus maps on a daily basis, and this includes doing metapoints for some of the most egregious examples of this. It's this use case that made me think that this would be a Feature that might make this a bit less ridiculous.
By the same logic of that argument, why bother with the Discard Extreme Values, or prevent extreme sets options? Both of those could indicate malfunction, and be implemented quite easily as a metapoint as well.
I guess I've kinda given up on "needing proof" that a communications interface / whatever is Broken. It almost always is. I'm trying to get Good Solid Data as best I can to run reports and analysis of the system as a whole, not to fight with disinterested inverter manufacturers about how to fix their kw registers.