Well it is good to see most of the response is positive hear.
From what I can see, not many are against the concept, but there definitely needs to be:
*A user-set maximum speed limit.
*The option to disable altogether (with the possibility of a slight speed limitation in heavy load situations).
*A statistic to show how much you are uploading, and rankings.
Touching on the mirror suggestion: I already have a system setup to manage mirrors, which involves two-way communication with the main server to ensure downloads are secure and throttled, as well as being automatically distributed. I previously made a call asking people who are willing to mirror maps, but the response was very small so find the p2p option a much more stable and future-proof path to take.
That said, considering I am almost exceeding my current bandwidth allowance (and can't afford to increase it further for the time being) I am happy to have offers for mirroring - just make sure you can spare at least 500gb of traffic and are hosting your mirror on non-shared hosting (unless you are sharing privately with friends). This means no godaddy/dreamhost/whatnot.