One quick comment. Overall, I think you're going about it the right one. However, this part, "3. Additionally: Partners A, B, C can authorize amount up to xxx level, etc..." should be changed from "Partners A, B, C" to some sort of "Spending Authorizer" role. So, in addition to the policy, add a part to your proposal to include a simple role to perform the function you intend, then just fill it with the role-fillers you think most appropriate.