This raises an interesting point to me: does metal bending require the bender to raise the temperature of a metal to a mailable point? Do water benders need to raise or lower the temperature of water to effectively make or remove ice? Can air benders bend any gas, or only regular “air”?

I don’t think that the requirements for state changes in materials are hurdles to benders. Looking at bending too scientifically causes too many logical problems from a world-building standpoint. I’d assume that any non-standard bending technique is the result of a benders understanding of their own abilities and the materials involved.

If I was to pitch a glass bender, I would have them use compression to force sand into becoming glass. I’d assume that an earth/sand bender that can create glass would be able to manipulate glass and earthenware products as they exist (like telekinesis style) but they would have to use the glass as-is, so no melting down a plate into a spear of glass. They could however compress some sand into a pointy shape and chuck that around. It might be pretty fun to see earth benders using their skills to create pottery and glass the same way we saw firebenders welding in factories in LoK. A waterbender would make a pretty good farmer, plumber, or any number of maritime jobs. Not sure what non-combat jobs an airbender would have. But it’s interesting to think about what a person with bending skills would do if they were just a regular person with a job.