Last year I was working on a new sort of blockchain that would enable instant transactions. I'm dumping some info here so it's searchable and maybe inspires someone or w/e.
The basic idea is that each TX has a small PoW attached and is 'mined' instantly. Larger miners (who are in it for the money) mine TXs with *large* PoWs and point back to other 'work heavy' blocks but also link back to these 'lighter' txs from regular joes.
Interesting - I've been thinking along similar lines recently, especially the stream of transactions. I was leaning more towards having each node 'sign' a transaction with it's stake as they get relayed between nodes, such that you get a fast forming, POS style consensus on each transaction as it passes between nodes. The only (and significant) problem with this is that it causes transactions to grow as they pass between nodes.