I think it's important to remember it's not just the key of a song, but the range of the vocal melody - the lowest and highest notes being sung and knowing if it's a singable range.
Also, I used to tag song keys in PCO with "male" and "female" but then realized I could easily make someone feel insecure about their masculinity/femininity if they sing higher/lower than most of their gender. I started using names, but if you have a ton of leaders maybe "Tenor" "Soprano" etc would be better tags in PCO.*
Sounds like things are moving forward!
Before you buy/build a bunch of XLR cables.. have you ever considered using Dante network audio?
I paid $30 for a software that allows me to use a single network cable to have 64 in and 64 outs. You also would need a $500 dante card for the board (https://amzn.to/2RmygWI) but i've been doing this for a while, and it's so awesome to plug in just a single network cable. You could also use the dante network to do virtual soundcheck (awesome for training volunteers!) as well as multitrack recording (great to get a solid mix for musicians to review their playing)
@jakegosselin was a little slow to hop on the Dante train but is doing this now too 😛