If the ability to pay pensions to existing members were at least partially dependent on utilising predicted 'current' contributions (contributions being paid at the time the pension was being paid out), the scheme would not be able to fulfil its pension-paying commitments in full if, due to changes related to the employer, those contributions cease or fall substantially. For that reason, I rather doubt that it is allowable to have a scheme which is reliant on 'current' contributions to at least partially honour pension commitments to existing members.