as someone who likes using steel monotypes i would approve of unbanning aegislash for steel since then vs fighting becomes a million times easier since kings shield forcing them attack drops.
but really whats so hard to understand about steel being so much better than ghost and it makes aegislash op? Just keep this one type ban.
If someone is having trouble seeing why aegislash is type banned try explaining how ghost has no hazard removal except defog drifblim, then proceeds to introduce the amazing abundance of physical attackers including golurk, regular hoopa, and dusknoir. Once they have recovered from that introduce them to the other side of special attackers, showcasing regular hoopa again and the surprisingly semi decent gengar and chandelure along with the amazing froslass. After that show them steel. Doublade, Mega Scizor, Excadrill, Heatran, Jirachi, Lucario. Once they see that steels offensive is infinitely better than ghosts show them how ghost practically loses to most types unless you are good at the type. Ghost already loses a bunch to dark, steel, water, fire, flying, ground and even ice teams according to
http://monotypeps.weebly.com/matchup-tables.html, and your best matchups? Enjoy the 58% win ratio against fighting since it quickly drops off, not even psychic is weak to ghost since they run meloetta or hoopa u, or even both. Along with that point out how steel absolutely dominates its good matchups, ice rock and fairy. Then proceed to show them how unbanning aegislash for steel would practically even out steel vs fighting, steel v physic would be dominated by steel, fire increases a bit for steel, ghost gets rekt, etc etc. And ghost has aegislash right now, look how poorly it does in its matchups. If, after all of this the user is still confused about why theres a type ban only for aegislash they are either obviously a troll or dont really understand competitive mons, and in either case its not really the type only ban thats only to ban...
tl;dr ghost is doing poorly and steel already does well, just keep the type ban and if new users cant see how the type ban is needed then they need to learn more about competitive pokemon
http://monotypeps.weebly.com/matchup-tables.html (is why i say ghost is doing poorly while steel does well, look at that nice 11 bad matchups for ghost and 11 good matchups for steel)