If the Contractor comes up with value engineering on a Contractor designed scheme then this is an exception to it being a compensation event. Therefore there would be no adjustment to he total of the Prices as a result. Under option C this would equate to the Parties sharing the cost saving in accordance with the ratio outlined in contract data part 1. Option A would see the Contractor get the full benefit of the saving.
However if it is Employer design and the Contractor proposes a value engineering scheme then this will be assessed as a compensation event - i.e. the Employer gets the full benefit of the saving for both option A and C (and the Contractor loses fee on the work not done)
Not necessarily a positive incentivisation on the Contractor to come up with good ideas for the Employer - but that is how the (unamended) contract is written.