I'm keen to know. One of the things I'm interested in, is creating decentralized currencies that is more secure than the current way of creating separate chains for each currency (this isn't secure if you assume a long tail of low hashrate coins). One such conceptual proposal I came up with uses a modified proof-of-sacrifice to mint new colored alts on the Bitcoin blockchain (https://groups.google.com/forum/#!topic/bitcoinx/mUb86IOeXdU)
However, it has some issues and would require considerable effort to implement. You still have to trust the issuer. Making it so that you don't have to trust the issuer, means you'll probably have to keep the whole chain to back-scan (which reduces scalability).
I assume, conceptually this would be possible with Ethereum? Before I delve too deeply into the coding, can someone confirm that this is possible with Ethereum?