Building-Block-API-error-messages-and-action-buttons

I consider WL's Building Blocks as a great way to generate (otherwise complicated) code. I tend to build more and more building blocks that do more and more complicated things.

With such complex code generation tools in place I miss two things from the current incarnation of building blocks:

1. Error reporting.
When something goes wrong during the code generation I can just throw an (ugly) exception.
If the generated code is bad WL simply says "could not compile"
Both are not very helpful. Would be nice if I could create some nice Error message which is shown in red close to the respective building block

2. Action Button
Some Parameters for my building blocks (may) contain complicated expressions. It is hard to enter such an expression without assistance. I'd like to have some (optional) "Action Button" close to the string parameter which opens a specialized GUI/Dialog - provided by my building block - and allows the selection of various elements for the string parameter. This could look and work similar to the "Make Optimizable..." button for int/double parameters.