We can aggregate all of 202.32/16, but we either have to lie to the NSF and claim all customers in that block are AUP compliant or all the customers in that block can't get to the NSFnet.
Please note that networks shouldn't be "AUP compliant" to be routed thru NSFNET, they only shouldn't send non-AUP traffic across NSFNET. Since they don't do that now there are good chances they won't do that in the future. NSFNET AUP does not explicitly state what kind of enforcement users should use (if any) and i do not see any sense in assuming that network number filtering is mandatory to be AUP-compliant.
Therefore, we have to break 202.32/16 into pieces and some service provider up the wire may proxy aggregate for us.
Don't do that! It will hurt many service providers most of which don't have anything to do with NSFNET AUP. Since your commercial traffic won't go to NSFNET anyway you don't run any risk of violating AUP. [As a side note -- here comes another technically unenforceable policy. AUP and Die.].
Or have I missed something obvious?
Yes. Enforcing NSFNET's policy with some (small) probability can prevent abuse of US taxpayers' money; not aggregating will CERTAINLY hurt the whole Internet (not excluding NSFNET) -- most of which wasn't built on US taxpayers' money. --vadim