There are a couple of topics to respond to here.
First topic.
Sandbagging does somewhat drive mods mad, but it is perhaps the least troublesome of all the problems we try to manage.
Probably the most “maddening” aspect of it is that people tend to report something as “sandbagging” when they mean “they can’t believe this lower ranked person beat them”. They have no evidence of rank manipulation other than this 
These waste tons of time.
I guess if we fully automated sandbagging detection, then we’d remove manual reporting, and this would solve that problem 
However, aside from that, to your points:
- We already have means other than IP to resist returning users who’ve been suspended
- We have automated cheat-detection that will be deployed against sandbagging (and others) once we finish tuning it for AI cheat detection
- In the shorter-term sandbagging will soon be handled by Community Moderation, which will improve out ability to respond to sandbagging reports in a timely fashion (this has been a problem).
Second topic
this topic doesn’t seem relevant to avoiding and punishing sandbaggers. It’s a choice about the rank basis for matchmaking.
This comes up from time to time - the most recent example is here .
If you wanted to tackle that topic, you’d do well to review the past discussions first.