Geomancy is channeling earth. According to previous lore, the denser something is, the harder it is to conjure or manipulate with channeling. It might be better to just say it can't be accomplished with earth and stone because they're too dense of materials, and leave this one out. This will also remove the worry Rias has with people being able to conjure solid matter.
Aeromancy is channeling air. I see we have a force school which can probably do anything aeromancy could, plus more. So, there wouldn't be much point to conjuring air. But if there were enough ideas to keep air and make it unique and different from force, I'm not against keeping it.
Now on to the two classics I am arguing to keep.
Pyromancy is channeling fire. It's not solid matter, and it is pretty straightforward in its uses. Mostly for damaging, as well as providing light and warmth. I think there should be enough cool ideas to make a whole school of spells based around fire. It can be the magic school used by the people who want to be spell users mostly for damage and combat reasons.
Hydromancy is channeling water. I'm biased about this one, since it's the one I want the most. It can be very diverse being in a liquid form and also utilizing some lighter forms like mist and steam, and pressurized forms for a few things. Here are some ideas.
- Water Barrier A channeled spherical barrier of spinning water around yourself. Defense against attacks, especially ranged attacks like brushing arrows aside. Also slightly affects your own attacks so it's a tradeoff. It would be great if it could be used on allies as well.
- Water Landing If you fall from climbing or other means, you can break your fall with the burst of water. This would have to be automatic to be useful, probably.
- Water Jet Knock over an enemy with a jet of water. Preferably also a version that just sprays off a friendly target to clean them without knocking over.
- Water Nova Knock over everyone in the room who isn't part of your group.
- Pressurized Sphere Bolt Throw a pressurized ball of water at an enemy to do some damage.
- Pressurized Sphere Shield Block attacks with a pressurized sphere of water, using Shield skill.
- Steam Jet Heat damage on an enemy. Preferably also a version to help friends warm up in cold weather.
- Fog Create fog in the area to help with hiding. Advanced version to put the caster in hiding as part of the spell. Very advanced version to hide the caster's whole group.
- Mist Cloak While channeling keep a cloak of mist around yourself to make it harder to see or target you with attacks, and maybe mask your identity. It also makes it hard for you to see, though.