Because I'm not a patient enough person to wait for the Creation Kit to come out, I went and wrote my own Papyrus compiler. Available on the nexus, I would include a link to it, but I probably haven't waited long enough after registering my account, so I'll leave it up to you to find Caprica on the nexus.

It supports what I believe to be the syntax for the new features present in FO4, and, as of v0.0.4 can also disassemble and re-assemble .pex files.

The Caprica compiler is also far faster than the CK compiler, as it is able to compile all 2.4k scripts for Fallout 4 in just over 8 seconds on my computer when compiling one file at a time, and 4 seconds when parallel compilation is enabled. (the current releases have parallel compilation disabled, but there will eventually be a command-line option to enable it)

Feel free to leave any feedback you have on it here, on the mod page, or on Github.