After re-reading all of these posts, there is a hell of a lot of pipedreams going on here.
I have zero-stop scopes and scopes without zero-stops, NONE of them will be on song when changing barrels, some re-zeroing/sighting will/is necessary. Just like 2 different loads rarely shoot to the same POI without some adjustment to the scope.
I have fired a 10 round group, removed the barrel, put it back on and HAND TIGHTENED it and had less the a 1/4" shift in POI, then had no shift when doing the same with a barrel vise/action wrench just nipped up past hand spun. Have repeated this several times, each time the result was a little different, but not much more than described
I have a self set rule that any one action/stock combo can only utilise a max of 3 barrels in different cals. To use more only compounds the difficulty in keeping track of the different zeros. I'm sure more could work, but for me, 3 is max. I must emphasise this is in regard to hunting rifles, not target rifles, which generally is a different kettle of fish. I have to remove stocks to change out my hunting rifle barrels, so this another factor in POI change.
Hell, even my F-Class rifle that has 3 barrels in 300 WM and 3 barrels in 264WM is hard enough to keep track of. All 6 barrels have the same headspace governed by the barrel shoulder, and all have less than .001" runout when on the action and spun in the lathe, yet they all shoot to slightly different POI. All of these barrels go in 26", 28" & 30" for different F-Class ranges and conditions. None use precisely the same load either.
The closest set of barrels I run is my 6.5x47 Lapua, changing barrels only shifts POI .2MoA, the same load in both barrels is used, I believe this is why the POI doesn't shift all that much in this rifle. Also, these rifles are permanently bedded and the barrels come off without the need for disassembly.
I like your ideas and theories, but just think you are asking for something that just isn't feasible, especially in regard to switching loads in a barrel and having a scope that can track upteen number of zeros.
Cheers.