In Cosign Consensus, the same decision is made by cosigners. Transactions are confirmed individually as users randomly select each other to cosign their inputs. There are no fees, and there is no inflation because there is no blockchain, no blocks, and no coinbase transactions. It's fully decentralized without staking or work, so it has no measurable impact on the environment.
Meaning consensus here will be made by local agreements between cosigners. Since the sender will have to Cosign along side some randomly selected cosigners and it is stated there are no fees, no block rewards no inflation, how do this cosigners get incentivized because it is obvious this will be a non-monetary participation?.
3. An attack seems possible in which the attacker creates transactions but refuses to cosign their assigned inputs. I think this was already suggested, but your reply was not clear to me.
When a cosigner is nonresponsive, the sender must replace their address. They must redact the first or previous transaction before publishing a new one to avoid having more than one version of a transaction in the mempool at a time.
Won't they be fear of delayed transactions? Won't we have increased mempool clutter if not properly managed?
How about risks of possible blackouts?.But my thoughts implementing automatic removal and replacement of cosigners might be a better approach, If possible flag non-responsive cosigners using a reputable system.