Comment by kanzure
Oh it's much older than 8 years... here is one such proposal from 2011: https://groups.google.com/g/enzymaticsynthesis/c/6GZT8zFNOfo...
I myself was bitten by a radioactive grad student in 2008 that was obsessed with this idea at the time, and have since learned that almost every major household name lab PI has thought about this in one form or another.
The archive.org mirror only goes back to 2017.
So let's say 2008 is the new infimum date, why do you think or suspect it is that DARPA is only interested in the idea 17 years later?
Especially since you consider it a household idea