Sure I am happy to answer these to the best of my ability.
I believe that my post answered the first questions in regards to the withdrawal root. In short it allows anyone to verify that the withdrawal root was created correctly which increases the transparency of some of the fault proof system. If we do not add this change, it makes it more difficult for everyday people to verify this part of the computation because it requires they need access to an archival node. I do not believe there is much valid criticism of this feature.
In regards the eip’s these are changes to the ethereum mainnet that agreed upon by the community. Optimism is maintaining compatibility with ethereum main-net but supporting these changes. If these changes are added or supported here then there will be features supported on the ethereum main-net that are not supported on optimism or OP stack chains. This presents substantial risks and I would consider good and standard for these upgrades to be added to the optimism stack, and that not adding them would present more risk. I do not know of much valid criticism of this upgrade of the top of my head but most of the discourse around what upgrades eth undergoes are well documented in a rigorous process that i do encourage anyone curious to look into.
In regards to the operator fee please see my comment here: Upgrade Proposal #14: Isthmus L1 Contracts + MT-Cannon - #10 by Jepsen
You are welcome to provide any criticism or feedback about the operator fee here.