In this post, I'm writing as a user, not a moderator.
Personally, I believe there's a fine line between GolfScript and HQ9+. Both languages are designed for golfing, but GolfScript is actually a general-purpose programming language (albeit one that lacks many useful features like floating-point numbers) that happens to use really short identifiers for its built-in operators, whereas HQ9+ is a language that's tailor-made to be good at three specific problems only.
So my question for you is, is your language going to be general-purpose? (That is, are your "cool built-in functions" going to be applicable to a wide range of programming problems, as opposed to being specific to a small handful of code challenges?) If so, great!
Also, you need to decide what will make your language appealing compared to GolfScript. One of GolfScript's strengths is that, compared to FlogScript, it's actually pretty easy to read: the operators are chosen with some care, and in particular, the author of GolfScript aimed to make most of the operators use punctuation rather than alphanumeric names (and given GolfScript's lexer, there is good reason for this). In contrast, in FlogScript, many operators use alphanumeric names and they are nearly indecipherable (IMHO).