I'm definitely thinking REST API here, we just need something similar to what masterchain.info and mastercoin-explorer.com already do, which is provide an API for viewing mastercoin transactions and creating new types of transactions. I'd ideally like to own the code that we create for this API, but reasonably, we could leverage or port existing APIs to node.js and that way we'd not be treading old ground. 

I think we could use grazcoin's method (sx to parse the chain) to do it pretty easily, at least, it seems intuitive.