I think in addition of the parser/compilation chain, a language is about having a good IDE.
The Pharo IDE depends more and more on the AST and not on the source code, so if your new language uses an AST polymorphic with the Smalltalk AST I guess you can have IDE tools for free (at least partly).
At least you can consider frameworks to build code browser such as Glamour as an available library to create a programming language.
In addition, Omnibrower, which is the default code browser in Pharo 1.4, can browse the code of any language. You provide Omnibrowser a language model and it browses your code based on your model.