I was navigating throughout all the wishes (as we constantly do), and found your wish lost here. We missed it during the last release of the Agile Platform 4.2, sorry! We answered to this thread and forgot yours...
Guess what, your wish has been granted! With the Agile Platform 4.2 you can now use Web Blocks inside Web Blocks. If you want to check it out, just download the Agile Platform Community Edition! It's free and yours for life.