ET Pro hasn’t been updated in a while anyway so think that wouldn’t be a problem.
Problem is how to keep a flow of good custom content whilst filtering out bad. To be able to determine whether the content is one or the other it must be tested thus allowed but then once it’s been ‘allowed’ how can you ‘un-allow’ it…
Perhaps if some guidelines were made, agreed by the community, in which custom pk3s of any nature had to pass these guidelines before being allowed then it could work that way but then how would such a process work and who would manage it?