and we will not be able to add more ever, or remove testers who are not logging in
Actually, the terms of the test server do say they can remove people who sign up but never participate.

A non relic owner is far more likely to point it out if final heaven suddenly starts doing 25k damage.
Relic weapons are not the only way to use the relic weapon skills. They are available as latents on a set of easy to obtain weapons.