To answer the original question: I often negotiate the rate with reservation managers (not need to go to GM really) for my group bookings, and they often taking a very flexible approach.

In the UK, reservation managers even told me for which weekdays they are willing to negotiate (for example, they can lower their price on Tuesdays and Wednesdays, but can't do anything on Friday to Sunday).

To negotiate earning level is very hard, because it's a system that they need to go through with IHG. Bonus vouchers are controled very tight in certain countries (proventing fraud by customers and own staff), it's not easy to get them in my experience. And I've never had a single reservation manager throw in some point vouchers as part of the negotiation.