Does Marriott have / have they ever had an award category that would allow you to pay less for a room, as opposed to going on a full award stay? I.e., x% off your bill for y points?

I am working in London this summer, and am currently staying at various 4-star properties - I would love to try out a few of the 5-stars (Park Lane, Ren. Chancery Court, West India Quay), but certainly don't need to take full award stays. Basically, I need to get the price of the 5-star down to that of a 4-star so my expense report doesn't get rejected