I'm interested if optimizations designed for bitcoin could work for monero, such as:
segregated witness / flexible transactions (http://zander.github.io/posts/Flexible_Transactions/) - is this even applicable to monero, or does it already have a neat transaction format?
xtreme thinblocks (https://bitco.in/forum/threads/buip010-passed-xtreme-thinblocks.774/) - is it even relevant, were there any studies done for monero block propagation times? Could it benefit from this kind of approach?