All those sound good.. BUT..
As my vote, I'd say priority one would be a script decompiler/compiler since we can't do that yet.
Yes, we have compilers, but that lets us change only what we have source provided for.. meaning any scripts inside the modules are about as good as being hardcoded for the time being.
If someone could come up with a proper decompiler for those, we could gain a lot of access we don't currently have.
Just my 2 cents.