Drop ranks, well lower the amount of ranks.
Honestly, aside from 'S-rank' there were no ranks at all in fairy tail in the terms of lettering. It's an assumption everyone has for some reason gone along with.
for canon let me use this example
- Spoiler:
At the beginning of the S-rank exam arc, EVERYONE was attempting to get a chance to be apart of the exam, if we make the assumption that those who did get in, Natsu, Juvia, Cana, etc. were all in because they were A-rank. Why was everyone else who was clearly not in their class of ability no matter how skewed and messed up Fairy tails distinction of power between character's is trying to get an 'invite' as we'll call it to the S-rank exam. Because aside from S-rank, everyone was a mage and that was all and had a shot based on their ability.
Basically my ranking system would be as follows:
mage(a majority of the site), S-rank mage(your elite group of mages who are your representatives with a lot expected from them), and a third rank where we would classify people like Gildarts who essentially a god.
This creates a lot of fluidity which creates good rping where the newbie can upstart and really get the ball rolling. Although there would need to still be some requirements set to get to S-rank and then to the unnamed third rank but there'd be a LOT less testing over ranking up because it wasn't something done on a daily basis by every single member of the site. Some of which would rank up to C and then just bail making the work kind of pointless for everyone.
If I wanted to REALLY use vague imperfect sources I'd send you to the fairy tail wiki guild rosters which only have two ranks overall, mage and S-rank.