Well, there are other crafters. Just none are as good. And I'm not sure if it'd work with Artificer due to the lack of spell slots to cast them from. Then again, I haven't looked at the Thought Bottle in detail. In any case I was trying to see if it was a factor of UMD or a factor of an Artificer specific class feature.
If the spells are cast from the Thought Bottle, then an Artificer(or anyone else with high UMD) can mimic the spellcasting class feature of an appropriate level Cleric. If the spells are returned to your spell slots-then I suspect it'd be no-go unless the spells are on your class list.
Well...let's have a look. *opens Complete Arcane*
Alright, first it's prepared spells only.
"Any spell she puts into a thought bottle is
expended as if she had cast it, but spells in the bottle can be retrieved at a later time to be prepared as normal."
Also, since "expended" and "empty" spell slots are different, and you can only prepare spells in empty spell slots AFAIK, this is nearly worthless. The only class that can truly benefit from this is...Archivists?