The described architecture is very similar to, and would specifically suit, StakeWise V3. By swapping StakeWise’s new liquid staking token (osETH) with CDP, you get exactly what is described in the ‘Merged LP’ing + Staking’ option.
StakeWise can enable any token to be minted through an overcollateralised debt position. By default, this would be its main staking token osETH, however it would be possible to add RAI as an asset to mint against at a safe LTV.
Idea 1 would still be the ‘simplest integration’ but it is the worst option by all other metrics. StakeWise V3 development is nearly complete and would unlock ideas 2 and 3 to allow for there to be no compromise in design. The StakeWise team is already actively working with the different DVT teams to ensure an integration with V3.
Whilst the V3 system is fully permissionless, it will also be able to cater to the needs of the semi-trusted oracle solution. All Vaults (CDPs) in V3 can be controlled/governed by the stablecoin provider and will have the power to whitelist node operators, allowing for permissioned/’trusted’ operators selected by the protocol to work alongside permissionless operators in a ‘safe’ DVT cluster.
This system would remove any reliance on a single LSD but instead allow for a diverse network of oracles (i.e. node operators) to stake capital in isolated/non-fungible capital pools.