It's just a matter of preference. You obviously feel that we shouldn't have to wear the gear to produce materia. You stated your reasons, that's all fine and dandy. You came to your own logical conclusions.

That being said, don't dismiss another logical conclusion simply because you disagree with it and think it's "dumb." It's not. It's the most logical scenario, hence why the majority believes that it will be a system in which you must wear gear to turn it into materia.

I hope they're a bit more creative with it personally. SE loves giving you "quests," that essentially have you kill 300 of ___ mobs or use ____ WS 300 times etc. That's part of why people have come to the conclusion that materia would be similar. There is a precedent.