[Sombre]

Why do people want to complicate it? It's purely a gameplay option; it doesn't need to be entirely realistic or cause some potentially abusable or newbie-confusing side effects.

Needing a commander to do it, or having to spend money to do it,... that's just going to encourage people to kill them off in inventive ways instead of disbanding (which is rather ridiculous) or increase the level of micromanaging, which is partly what a disband button would be there to reduce.