I am sure the maintenance business will lobby for the maximum gold plating, as I would fully expect most of them to do.
But one can forget who one is ultimately serving: the customer.
If the customers chuck it in, which they are in big numbers, the game is over anyway.
If one could install stuff based on a US STC (which BTW will IMHO never happen; just look at how EASA hates AML STCs, which would result in mass unemployment in EASA and part 21 companies) that would take out a lot of approval business (which most avionics shops don't benefit from anyway because they buy in the paperwork packs from some of the bigger ones) but it would generate a lot of business on the actual installation work.