Good roundup there.
But back to the original question, I think things are only going to get more "interesting"
For so long, we had a few RCDs (and other bits and pieces, but mostly RCDs) where the instructions were to disconnect them and do IR testing at 500V. With maybe one or two RCDs in a split board that's not too difficult to do - but a board full of RCBOs ? Now the model forms have a place to mark voltage used, and 250V is specifically allowed where 500V might damage equipment. Before this change, I was of the opinion that disconnecting to test at 500V was "not always a good idea" - think of the amount of disturbance in a CU when it's all RCBOs. In my rental flat, during periodic testing I found a high resistance neutral in the RFC - which I eventually tracked down to the connections in the RCBO. I'd specifically done testing at a socket as the RCBOs I used are not very easy to work with while the socket allows easy visual inspection of the connections when putting it back together. Had I done testing from the CU, I wouldn't have found the found, and it's quite possible I could have put it back together with the same (or another) fault. But as long as I use the old "press and hold the button, watch the needle" IR tester, I can test the IR of the whole installation in one go as long as I use 250V and one polarity (the RCBOs have a resistance to earth in the other polarity) - if the whole installation comes up with a reasonable IR, then every circuit in it must be OK on it's own.
For a household of "smart" stuff, as Brucie used to say, good game, good game
I think you'd struggle to actually test anything other than the mains voltage stuff - and again this would probably have to be at 250V to avoid having to dismantle the whole installation. Then you have the problem of testing circuits that are switched by the smart stuff - so you can't test (eg) a light circuit all the way to the rose/pendant just by flicking the switch on the wall, and it might not be possible to switch it on via the "smart" gubbins while leaving it powered down for IR and Zs tests.
As for the ELV stuff, other than perhaps IR testing Class II devices to ensure that the ELV side is actually isolated from the supply, I see little you can actually do with them.
A little topical for me as I've recently been thinking of more work for myself at home - as if SWMBO doesn't complain enough about the jobs I haven't got done and those I haven't finished
I bought some scaffolding for doing those "stuff I don't like doing off ladders" jobs. Put it up to sort out the light on the back gable, and ended up using some conduit to change from one very high up PIR/floodlight to a PIR and two LED floodlights mounted less high up. Then I get to moving round the side to sort out the guttering, and remember that the light round there doesn't work. Then I start thinking that if I pick up a feed from the cable that feeds that, I can change the switch in the living room to override PIR on the back instead of switching the feed. And then while I'm doing that, realise that if I use a tee box instead of a bend, I can drill through the wall and end up in the boiler cupboard which opens up all sorts of possibilities. So now I;ve gone from "fix the light" to a conduit run across the gable, round the side, along under the eaves, and into the boiler cupboard - with tee boxes for the two PIRs and three lights
Then I started thinking about more fancy lighting and whiel browsing for RGBW lights, came across a manufacturer offering what they call "series" lighting which is basically the RGBW LED mitter with no drivers. So now I'm thinking that at a future time, I'll pull out the 240V wiring, pull in some ELV wiring (remember, got all the conduit in place now), rip some fittings apart and replace the innards with some bare LumiLED RGBW emitters - and I can fit DALI controlled 350mA or 700mA drivers in the boiler cupboard and have mood lighting in the garden
Bet SWMBO won't be impressed though - that's the major limitation for stuff I do, the WAF which isn't always positive