Basically, the logic here isn't that what you guys want is necessarily a bad idea in and of itself, but rather the repercussions it will bring. Due to the fact that only about 5~10% of the playerbase will ever actually own a finished relic/mythic/empy, they are a desirable item people want to play with. Thus, while you want this:
Add Them: Those who can test but don't have the weapon on live are able to test them for possible new effects in one last update before they launch, after which they won't likely ever receive any more changes
but what you'll get is this:
Add them: number of slots on the test server ~500; ~50 are occupied by individuals who actively test new material in a proper manner, knowing what they're doing and how to do it, ~450 are occupied by Joe-Shmoe-DomaruSam who log in once or twice to play with a relic/mythic/empy and then never log in again but stay on the test server, preventing any new testers who actually know how to test from getting in.