That's a good story. If you support the status quo, that's the story you tell. But it isn't accurate.
If you have any kind of rough consensus, or even just lack of strong consensus to oppose a change, then support of the majority of miners is sufficient to make any change you want. That's the reality.
Yes, that's true. But the miners here are not changing things right now. They are sticking with the 1MB version which exists since the days of Satoshi because
Maybe. Or maybe they are just doing it because it suits their economic interests to keep blocks small, as TPTB said. I consider that quite plausible, I'm surprised you don't.
if either proposal is followed without consent, you have 2 competing coins / you have doubled the monetary base
Incorrect. (I think you meant "without overwhelming consensus' rather than "without consent"?)
@TPTB you can't really have it both ways. Either the miners hold the upper hand or the developers do. I think it is a former, and given that you don't need overwhelming consensus, there is no 'design by consensus'.
Now if Bitcoin actually worked in a more fully decentralized manner then miners would not hold the upper hand and then you might get something closer to design by consensus.
EDIT: What satoshi was shooting for by his own words was neither design decisions made at the whim of a mining cabal nor by an overwhelming consensus of developers, it was "set in stone". It wasn't even close to achieved.