All good points. In order:

1. The newest BOINC credit system is more sophisticated, but still has other problems. Regardless, this is a problem that affects the current distribution mechanism as well. Fundamentally, this is something that BOINC needs to take care of, and is beyond anything that can be done Gridcoin-side. It's not exactly clear how this problem would affect rewards under the current proposal, similar to point 2 of "Impact of the Changes".
2. That's a problem. I wasn't aware that the coprocs was that bad, I'll have to think about that more. When the process is a bit further along it would be great to have your insight.
3. Those inherent differences manifest themselves in higher/lower granted credit per unit time. It might not be reflected in M and thus the normalization, which is definitely sub-optimal (and means that the normalization is further away from the "ideal"), but users with better configurations will still receive more GRC.
4. With enough data and a good selection rule as discussed at the end of the "How is M built?" section, this problem should be mitigated.