There are no performance implications as no logic runs unless triggered, but states do take up some memory.
However, if this is primarily for dialogues and not any of the specialized things that Lua can do, you could look into TXR? It’s 100% GML and can yield at any point by design. People have modified it to have custom syntax for dialogue trees before, and some of the recent additions to base source code (like select statements) aid with that.