I don't know how I feel about nodes deciding block size. Seems like a good idea but I also see the potential for a group to control the blocksize..
I skimmed through this thread and didn't find it mentioned that the blocksize can already be changed by the miners/pools. Currently most of them have it set to 1MB so that's what they went with. by defaut (for some reason) it's at about 750KB (in core) so there has already been an increase at some point.
Other than increasing blocksizes, using segwit and attempting code to merge scripts (which may make new hacks) I don't think there are any other ways.
If BU will gain more support and SegWit will clearly be not going to happen, then i imagine that Core is prepared to adopt a new strategy where they make a BU like suggestion in order to give the mines and user what they want but on the terms of core (so maybe minor changes compared to BU). The pressure would have to be big enough and adopting BU just around the corner to see this.
Yes, but changing the blocksize setting on your copy of bitcoin core, if you're a miner and many others do the same, will increase the blocksize. The network is configured by how nodes function. There is no central server that dictates the blocks are too large and rejects them. If enough miners change their blocksize limits then the limits of the entire network will be increased (if a small percentage of miners still use smaller blocks then they will also be added to the network but there's quite a good incentive to increase the price → you get more bitcoins from mining as a reward).
That's not really true? My bitcoin core software is set tothe default of 750kb because I don't mine with it and it syncronies with blocks greater than that amount. It doesn't reject the blocks, like you suggested. However, it would take quite a lot to get the majority vote of the mining power (around 95% it was for segwit) before the blocks were acceptd so of course the majority of miners have to accept the new block. But, if companies like Bitmain, Bitfury and the other giant mining firms considered changing that then the blocksize could increse (but it'd still take the 95% to change that).
I just had an idea that might help to understand it.
Our week has 7 days. How many days do you work? 5 out of 7 is the default setting. Some people prefer to work 7 day a week because there is much work to do. If someone would come along and ask you to work 6 days a week, you would not like it or not do it, but you would understand what he is talking about.
If someone would want you to work 8 days a week, you would just tell him, that this is not possible, since 7 is the maximum. Society would have to agree first that a week has now 10 day. And if 95% agree on that, then 8 days of work per week would be possible. The 5% that did not agree on the 10 days per week could try to do their own thing, but i think everybody has an idea what the consequences are for them.