On the Blockchain Pruning:

Why dont we implement a Finite Blockchain?
This has been discussed for bitcoin for a longer time and one of the biggest hurdle was to implement the accounts tree as bitcoins can be saved offline.
This is not hte case for NXT, perhaps it could be used to solve our problem.

Here is the paper: http://www.bitfreak.info/files/pp2p-ccmbc-rev1.pdf