Time to find a new engineer chairman: AC21-08 provides very specific advice on how to incorporate commercial off the shelf components into modifications and repairs.
Dunno Progressive.
AC21-08 was only issued Feb 2015, and does indeed provide specific advice as you say. My reading of it seems to concur with my Aeronautical Engineer EO guy - that the cost to incorporate COTS parts in any new EO is extremely/prohibitively expensive. Better to completely rejig any design to use PMA parts.
Any EO guys here?