The whole consensus depends on the very first block hardcoded in the wallet you get.
If you want to reduce the size of the blockchain, you still have to download the full chain first.
Otherwise you have to trust a thirdparty, and usually centralized.
For example, we, as the core team, can publish a new ‘genesis’ block containing calculated balance of each account, in this way, the blockchain is pruned.
However it’s centralized, because of the privateky.
DAO is not possible here, we don’t even have a trusted blockchain here.
So, pruning blockchain in decentralized way is rather difficult.
As I wrote in the IPZN’s wiki, an archival block (i.e. evaluated balances) is generated periodically backed by the same consensus.
When a user downloads IPZN client somewhere, the initial consensus, the most recent archival block, is inclueded.
After syncing a few new blocks, and verified, the blockchain is pruned locally again.