I don't think ARIN is planning on giving out more less a /48 but more than a /32- at least that was the impression I got. End sites get a /48- ISP's get a /32 or larger- and that's it (I could certainly be wrong). As such, deaggragation in the /48 block should not be an issue because no one will have more than a /48 in the first place.
Yes, you can get a prefix between /32 and /48 if you can justify it. That is certainly in line with the policy which resulted from proposal 2005-1. You are of course correct- I misread "The minimum assignment size is /48" in terms of prefix length (ie minimum of /48- could be /56, etc.) which is not what was meant. The very next sentence should have clarified that for me but I probably skipped over it. mea culpa.
I'm looking forward to seeing a realistic justification from an end user for more than a /48 :) As an aside- what is the address block for PI end user assignments from ARIN? (I can't seem to find it and 2005-1 only mentions a "distinctly identified prefix" without any mention of what that would be). The Microallocation blocks are: Internal Infrastructure: 2001:0506::/31 Exchange Points: 2001:0504::/31 Critical Infrastructure: 2001:0500::/30 (all of which are /48's so far). But I see no mention of end-user assignments (unless they fall into one of the above categories- though I don't see how). -Don