Ah, I forget about the 1 piece cranks on roadies. On my mountain bike crank there are only 4 bolts to remove the ring, easy as can be to change out. And the rings I use are only about $50, so it isn't a big deal to have an extra one on hand for the mountains or whatever. I have a buddy who has the shimano electric on his road rig...it is sweet! Expensive, but sweet.On a road bike that is such a pain man. The chainset and front drive side crank are often one piece meaning you have to hold a few of those in reserve and depending on if you have a power meter some meters are built into the chain set. Where as changing a casette is just a case of taking the back wheel off. Hey dont let me sound like I know, I barely ever do either because I have plenty of gears and I am no mechanic.
Although a 12 speed would give you great variability I agree without any need to change. Even an 11 is pretty good. Just go mid range on the front ring and give it some more RPM between if you are finding you are halfway house.
Either way. Front mechs arent going away anytime soon on the road. I do want an electric groupset that matches when you change the big ring. That would be cool. A pet hate is having to match the two yourself, I want smooth transitions. A single front ring would fix that or di2 or SRAM red both offer (I think) matching when you jump the big ratio. I would like that. They cost more than I paid for my entire bike though... next year maybe.
On mountain bikes, another huge benefit of the single ring is that you can run the chain a little tighter. When you have to have enough chain to accommodate multiple rings, you end up with more slop. With the single ring I get way less noise from my chain slapping my frame. I like the simplicity of it. And getting rid of the front shifter opened up a spot in the cockpit to put the lever for my dropper post.