On liquidity, as I mentioned above, I agree that on-chain liquidity is paramount for any asset that’s listed as collateral. And given the preference for Aave V3, I’d expect that the community would vote to isolate and cap the supply in line with the on-chain liquidity.
To answer the second question, Coinbase leverages Coinbase Cloud and several external enterprise-grade infrastructure operators for ETH staking. Leveraging multiple providers reduces the risk of correlated downtime or slashing events that could be caused by any one operator. Beyond node operator diversity, these operators run multiple Ethereum clients, using multiple hosting environments, in multiple geographic regions, all in the same effort to reduce the risk of a correlated slashing event.