I can only speak from personal experience, having worked both for business partners and as a customer (currently on the customer side), but I would think that if you spoke to the BP's salesperson for your acccount or the sales manager, they would get the sales engineer to discuss an upgrade, i.e. sale of more product, for no cost.
You might want to ask the question of another BP and see if you get a different answer. The other BP may also be able to help with the service issues you mentioned. I have seen higher levels of BPs, Platinum / Diamond, get a faster response from Avaya.
We have been able to work with our BP to get issues with PLDS for downloading software mostly resolved by their escalation within Avaya. It had to do with the timing of changes to Product IDs not being updated in PLDS. Avaya made changes to the Product IDs in the middle of our maintenance contract that caused us to lose download entitlements for a couple months..
Richard C. Browne, Jr.
Telecommunications Engineer
MAP Communications, Inc.