I'm pretty sure this has been discussed before, but I can't find the discussion(s).
One of the problems with (most) of the blockchains is that it is not scalable at large numbers. I don't want to get into why.
Possible solution: light client with random number of blocks (1M seems reasonable). This would solve the client side problem and reduce it to a problem to find "likeminded" clients. Every transaction would still need a minimum of X full clients to confirm the transaction, but it would address the scalability issue.