I haven't yet done any, but I am about to do so.
I have used script components to parse complicated flat files (not X12) and output data flows, and reading data flows to write output files.
I have also created non-SSIS dot-Net programs that make DB calls and put the results into X12.
Should be simple to paste the latter code into a script component, tweak it to make VSTA happy, and steal bits of my older work from the former.
I guess I'll know in a week whether my "Should be simple" was mistaken. :-)