Okay so best Champions:
https://www.letsbeef.com/forums/showthread.php?t=128666
Quick skim and I see like 12 (Not all GC's) that could battle which isn't bad actually.
Then you look at all champions ever (text):
https://www.letsbeef.com/forums/showthread.php?t=99225
You can add like 4 at least, it'd be feasible but I don't think you could do all GC's, you could do like a Champion of Champions Tournament just to fill the spots, otherwise you'll only have like 8 (if that) obvious active GC's which wouldn't be that interesting. Plus if you expand on that and allow 2nd or 3rd place folks in there you get a bigger pool cause they're often overlooked just cause they don't have a title but they were so close to getting one.
All audio champions if y'all want to explore that:
https://www.letsbeef.com/forums/showthread.php?t=103349