@Governance_House Our recommendation is to take a conservative approach with regard to enabling an asset as collateral. An asset can always be enabled as collateral, but it is difficult to disable an asset as collateral.
Borrowing rETH is a valuable component of a healthy market. While it is up to the community to decide whether an asset should be borrowable on Aave, there is not much utility to only enable the supply side (i.e., sans collateral enablement) with borrowing disabled. Not enabling stETH as a borrowable asset is due to technical concerns on correctly implementing rebasing assets on Aave rather than on the market risks.