Forgive my cynicism, but combining different Main Options under one contract does not seem a very sensible course of action to be honest. The payment provisions will need to be very carefully and comprehensively amended to allow it to work in practice, including making some significant changes to Defined Terms ie: Prices, Price for Work Done to Date, Contractor's Share, etc.
Assuming there are no design responsibilities, why not procure the materials under a supply only contract and then let the installation works under a Main Option C contract, with whatever incentivisation you have in mind..
Assuming there are no design responsibilities, why not procure the materials under a supply only contract and then let the installation works under a Main Option C contract, with whatever incentivisation you have in mind..