CPF FAQ doesn't have enough details on the property pledge for this scenario or I can't find it, best to write in to CPF Board to confirm this is doable.Just before opt-in for cpf life, pledge property and withdraw BRS leaving FRS for cpf life standard plan.
Assuming the above is allowed, for Standard plan, the RA is used fully for the LIFE premium which goes into the Lifelong Income Fund for risk pooling.After cpf life standard kicks in, use the withdrawn BRS cash to top up RA for AMP.
I think the AMP default end period is 90 years old but can be changed upon request following what RSS does - but I don't know for sure, so please write in for written confirmation before proceeding.
So basically the LIFE premium for Standard plan covers longevity risk whereas the AMP portion payouts based on the member's chosen duration or until 90 years old.
End outcome (from a returns' point of view) depends on the actual life expectancy and whether the AMP period can be adjusted and whether there is sufficient liquidity elsewhere so my honest answer will be - I don't know.