You are not (and neither am I) where a valued member will be excluded from the roster because of class. While you can't have 11 demon hunters, having 1 to much of a class is not gamebreaking. In my guild we take whatever team will have the best chance of killing the boss, be it player skill/setup. On some bosses specific classes are OP - but in most cases you can get around them. A holy paladin is insane on KJ Mythic, but we still managed with a resto shaman healing the adds instead.
We keep a roster of ~27 players, which gives alot of flexibility, as well as variance in classes. There are some things we have to much off, and to little off - but overall it is fine. In my experience, you rather want to many raiders than to few - even though that means you have to bench people more often. While is it not fun for the players and difficult to manage, it means you can adapt to changes happening, and always be able to set a raid.
I would suggest talking to your co-officers about what goals you have with the guild, and afterwards explain it to your raiders, so they know where you are heading as a guild.