Pretty sure this is being worked on! If you're really interested I can check with an ex-colleague who is involved in Free Pascal.
Hmmm, can Lazarus be used to build a "GUI browser"? For example, can one send a "create button" command or tag to it and have it draw one dynamically? What about new panels and forms? How "meta" can its GUI engine be at run-time.
Yes it can do that. That's how the IDE works and displays the GUI designer.
Can you recommend any documentation on the "meta" angle? Most documentation I find assumes the creation of "static" widgets that are activated or hidden at run-time (or at least act that way).
Yes, it may be able to. At least, Delphi, the idea (and language) of which Lazarus is based on, was written in itself, at least for v1, I've read. Probably for later versions too, because Object Pascal (although IIRC the language is now called Delphi, like the product), is a powerful general-purpose programming language, with OOP support, module (units) support, and even some sort of generics (IIRC) in later versions.