Thanks for writing up the proposal! A few a points/concerns on my side:
First and foremost is the on-chain liquidity (conscious this was also discussed above). Liquidity in the Curve and Uni pools is not sufficient with respect to the supply of cbETH. As things currently stand, there will be too much reliance on centralised liquidity to facilitate liquidations. Aave cannot onboard an asset where liquidity depth is so opaque unless there are supply limits in place which are based off the measurable on-chain liquidity, imo. During events like we experienced earlier this year, centralised entities failed/halted trading and showed they cannot be relied upon. stETH was also listed on multiple centralised exchanges during this time and there was no indication that the CEX liquidity helped in any way. DeFi/DEX liquidity however proved its robustness/importance.
Second, can you shed more light on the node oeprators/decentralisation? Depegging from liquidations is one key risk, but the other is liquidations from slashing/penalties. I am concerned that a token like cbETH will increase systematic risk unless there is a sufficiently decentralised network of node operators.