In 2013, a paper I contributed to offered a solution to the ever growing blockchain delema: a finite epoch. The solution is similar the one Chaum used on Digicash. It would fix, temporally, the blockchain to include only transactions for the past 2 years, for example, thus creating a blockchain of tractable and predictable size for affordable full nodes.
More recently, I've co-written a paper proposing a distributed service solution that could solve thin wallet privacy and security issues without needing to trust individual full nodes under the control of others.