First of all, while it's true that "more important tasks" like event info and current ongoings are handled with more activity than quote and lore translations, the real issue is the severe lack of help in the Wikia. It's a far cry to find a user who wants to help here and is comfortable with translating Japanese into English.
Google Translate and outright copying quotes from Nutaku is a cop-out. The former is just outright dumb since GT can't even make a coherent sentence. The latter is almost plagirism. We claim to be a Wikia specifically focusing on the DMM version of the game, so using Nutaku stuff (at least without crediting) is a no good. That said, I'm not saying it's ok to use Nutaku's translations so long as you credit them; like the Dipladenia screenshot, some of those translations are really rigid and I feel like someone could do a little better...
Regarding the names used in quotes, use the Wikia names. If someone calls out to ヘレニウム, then we say someone called out to Sneezeweed. But if the character uses her own name to refer to herself, that's when you can take a spin on the localization and either use her name or "I/me/my" (personal pronouns). An exception like Glory of the Sun is fine the way you described it because, most importantly, it sounds fluid.
Finally, regarding the translation of danchou (団長), I've always used the word Leader because the word refers to the head of a group or organization. It's also probably the shortest and simplest translation for the word. Grandmaster is horribly awkward imho. For one, I would have the tendency to write it as Grand Master which would ruin the consistency in the Wikia (there's a similar problem I would like to fix regarding "Crystal of Life" and "Life Crystal" for example). Grandmaster also implies that the player is a master of something, but there's no implication of that whatsoever in the game's background. Knight Leader and Knight Commander have the same implication as "Leader" but add a word of negligible usefulness. Liege is erm... Apparently correct? It's not the first thing I would've thought of, though...
A lot of subjects got thrown around in this discussion. If I missed something, tell me.