A thread to post ideas any coin is free to use.
Idea #1
a) Divide blockchains into 6 month segments.
b) Reduce each segment down to a list of the final balances of all the existing addresses.
c) Each client would download alternating segments so that 50% of each client's download was "summary" segments and 50% was full segments. For example half of people would download the first full 6 months of the blockchain and half the "summary" version.
d) A person could opt to download the full blockchain if they want.
These huge downloads are getting expensive.
Eventually I might summarize other posts below in the op.
I'm supervising a project (as part of Dogecoin) looking at blockchain "regenesis"; creating a superblock that contains a Merkle tree root for the UTXO set, so that if you have that block and the UTXO set, you don't need any of the preceeding blocks. Clients would then contain a checkpoint for the most recently superblock, and you have to trust your client, but you already have to trust your client anyway.
It's a long way off (it's not even formally started yet), but I thought people might be interested in knowing what's being looked into.