I honestly think of this all of the time. I think I am now more fluent in mIRC Script than any other language (although I know Qbasic and Java pretty well). Every once in awhile I think of starting to write a program of some sort that can run mIRC Script without the aid of the actual mIRC (taking out of course the actual IRC functions :P). mIRC supports the majority of what the other programming languages do, and for the things that it doesn't, there is the dll support lol.
And actually, what I'm mentioning is not a compiler, rather more the approach that Java had, an interpereter. I'm picturing a scripting file, that is executeable through some sort of program running in the background (like Java's runtime interpereter), that way whenever a user double-clicks on the file, they can be run. The only difference would be that all of the code would have to have a specific 'main' alias to run as it starts.
A lot of the programming I do in mIRC invokes the dialogs and sockets heavily, and very little of my mIRC Scripting has much to do with well, IRC, anymore (mostly because the only computer I have around here with mIRC is not connected to my currently dialup connection). Thus I think it would be cool to see my Webserver script to run without the big mIRC window behind it