* Anyway, the best chain is selected by amount of work in it. Thus rejected blocks potentially could be included into the blockchain, but only if most of miners (>50%) break the rules and accept them. Therefore, during the evaluation of PoW for a chain, nodes shouldn't count these blocks until they are followed by two or three valid blocks. For the same reason, it makes sense to limit one-time increase of block size in comparison to the average size of the previous several blocks, say not more than twice.
No. This is a horrible idea. It gives miners absolute control over the consensus rules. The consensus rules will stop being consensus rules and suddenly become Miners Want This Rules. Making such a drastic change will allow miners to change whatever rules whenever they want. That is completely antithetical to Bitcoin and completely defeats the purpose of full nodes. The point of running a full node is to ensure that miners follow the consensus rules, not just to have the entire blockchain. Your proposal completely removes that check on miners' power.
By your proposal, miners could decide that they can make a transaction which spends all of the Bitcoin back to themselves, put it in a block, and make a ton of money. Or miners can remove the block subsidy schedule and just make as much Bitcoin as they want out of thin air, and everyone will follow. This idea is just plain stupid and simply hands over all control of Bitcoin to the miners, instead of splitting it between users and miners.