I am now looking at the Red programming language [1] for exactly this, but it does not have the libraries of C++ or Tcl. Still it is under 1 meg complete with libraries and it is homoiconic, cross-platform, and has a REPL and a systems language Red/System for going low level. The GUI and UI DSL and drawing DSL work on Windows and Mac for now, with Linux close behind.
I like Lazarus a lot. I am not a fan of Pascal though, and Red is under 1 MB batteries included. I like how it seems a cross between Lisp, Forth and other languages.