Sounds somewhat overly complicated.

[i]n[/i] posts per [i]t[/i] minutes is probably one of the easier systems to use and implement.
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And we do agree that any system where non-mods are permitted to issue anything akin to bans should be heavily restricted. 
High post counts + long membership is a fair requirement to have such power.

Sure, this would mean that quite a few people wouldn't be able to have such power, but it would still ease the burden of the mods.
Also, a simple safety measure like the one we mentioned earlier (that it takes several "empowered" to actually ban), would probably be wise to prevent revenge bans. And of course all such should be reviewed by mods later on.