Brendan's post also mentioned problems with Ventriloquism. How could we fix that?
This may be harder, because honestly, why aren't we just using mundane ventriloquism as a learned talent? 5+ on 1d6, modified by Int or Wisdom. As written, the spell doesn't really trump anything. In fact, since the caster has to be close to the planned target and has to recite an incantation first, wouldn't everyone know what was going on? An Illusionist variant, with an option to use concentration only, no incantation, could work, but that's another topic entirely.
Magic Mouth is actually a much more interesting spell. It is delayed and can thus trump the need to be physically present to speak, so it can be used to set up interesting tricks or distractions, or deliver messages. I'd actually consider moving this to 1st level and dropping Ventriloquism.
Another spell, not listed in Greyhawk, is Audible Glammer, which is a magically-produced sound. If Audible Glammer exists, there's no need for Ventriloquism at all, since an Audible Glammer can do anything that Ventriloquism can do, and more.