If the script was interpreted, then you could pause, change, and continue.
However, the wdl file is compiled. You have to recompile the whole wdl file before the new file for the engine becomes effective.
I'm guessing, but I suspect the engine loads the compiled (object) wdl file into memory before it runs. And I doubt it looks back at the disk. Which is how A5 is able to run much faster than an engine that interprets scripts....
How do you reload a new compiled file? Build to compile, and then RUN. Which is what you are trying to avoid, I know.
I think you either get flexible, or fast.
I'll take fast.... 