1) Justify why we need a heavy bureaucracy such as ARIN for IPv6 numbering resources,
Because the members of ARIN (and the other four RIRs) want it that way. And because nobody has yet made a serious proposal to ICANN that would replace ARIN.
2) Tell me why something like the old pre-depletion pre-ARIN model of InterNIC and just handing out prefixes with substantially less paper-pushing wouldn't result in a cheaper-to-run RIR.
Because the ARIN members, who pay most of ARIN's fees, are not complaining about the level of those fees. This means that they think the fees are cheap enough, or else they would demand that the fees be changed. All ARIN fees are set by the ARIN members. --Michael Dillon P.S. When you send your proposal to ICANN, please post a notice here on the NANOG list so that we can all go have a look at it.