Instead of carrying full blockchain, why not this solution?

Summary:

client will include only last 1.000 full blocks and 10% of all other blocks.

Details:

for last 1.000 blocks : 100% include

for all other blocks (before these last 1.000 blocks) decision either
 A. to include or
 B. storing the following info from a block
        - block number
        - hash of block
        - list of (first 16 characters of) all bitcoin addresses impacted by this block

choosing between A and B is based on some randomness and if it has an acceptable distribution (10%?) on the network (using a Distributed Hash Table, just like with bittorrent?)

now, if a client wants to know the "balance" of a specific bitcoin address, it can just check which blocks to download (P2P) to provide a solid confirmation of this "balance"

to get an immediate non-solid indication of a "balance" of an address, consumers can use a trusted party website (which has downloaded the full blockchain)