An interesting article to say the least.
I think that customer engines need to be identical to the works team, that is an easy one.
I think the less aero involved is a good idea. What would make the most sense to me in that area would require a bit if research by an outsider in all probability. I think that it would be wise to reduce what ever it is, and it may involve several factors in the aero package, that reduces the ability of a following car to get close to the car ahead in the corners.
We have been listening to drivers voice their problems with this - losing down-force in the corners, preventing them from being close enough in many instances to exit a corner close enough to put a move on the car ahead before, or at the next corner.
Years ago, before the aeros got so high tech, this was seldom, if ever, an issue. I recall racing as recent as the early 2000s, in which cars would even over-take on the exit of a corner, having benefited from following the leading car closely through the corner.