I’ve been using custom names for trust levels with no issues outside of the aforementioned conflict between an existing username and the new group name (resolved here Trust_level default name?) Isn’t the whole point of the custom text section on the admin menu so that you only have to make one change to alter the zillion places in the UI the text is used?
Based on my experience, changing the name of the trust level is an easy way to give your forum a more coherent theme and is just more fun.
Trainer > Ace > Leader is a lot more meaningful, on brand and fun for my community than trust_level_1 > trust_level_2 > trust_level_3