That would also be a reasonable approach, sure. Maybe it'd be better. But our approach hasn't caused any problems as far as I'm aware, I've never seen anyone say that we didn't have the pronouns they wanted, and I'm confident that if they did the mods would add the option for them, like what happened with doe/deer. We were just concerned about opening up an avenue of misuse, and it's very rare that someone uses pronouns not on the list so it's easy for the mods to accommodate when it happens.
:::spoiler Here's the list fyi
none/use name
any
comrade/them
des/pair
doe/deer
e/em/eir
ey/em
fae/faer
he/him
hy/hym
it/its
love/loves
she/her
they/them
undecided
xe/xem
xey/xem
ze/hir