-snip-
Having artificially limit does not provide any meaningful prevention. Nodes should have better rules for that and there are already antispam filter rules you can use.
Should have or are implemented? Examples?
-attack on person no real argument-
The only valid argument regarding bigger blocks is blocks relaying. Sadly we dont any useful discussion about it on this forum. You can search elsewhere for that. Its been discussed and being tested right now.
BIP101 is not a rush, its already conservative. The blocksize limit debate has been going on for more than 2 yrs now. Slowing down is just a dumb reflection of the topic.
Increased costs for private run 24/7 nodes might not be an issue for you, but for me it is. Without pruning I could not continue to run my node. Just because its not an issue for you does not mean its not an issue. This is exactly the point. The goal is to keep a higher number of full nodes because they are important for the network. O(1) propagation is discussed and tested yes, but from what I read not read to go live. Same for pruning with wallets.
BIP101 addresses none of the issues, but TX spam related delays. The most recent attack (sig OP spam) would still be possible and would still have resulted in higher fees, there are over 10k TX in backlog constantly, yet not all blocks are full. This is not solved by just increasing the size. Its also dangerous to just force a fork on the live network as the last test on testnet have shown. If miners would switch to BIP101/XT en masse without further agreement from the rest of the bitcoin community it would very likely make the network unusable for weeks.