> Internal tools are terrible in the sense that there's no knowledge base to pull from, beyond internal. This limits the chance of the tools actually being use or even understood.

Not been my experience at all. The business people absolutely know that tool inside and out, just because your development teams have high turnover doesn't mean that tool hasn't been taught to everyone who uses the software.

In fact, my experience is that when a bug is introduced unknowingly the business side can describe you very concretely what it used to do and what they want it to do.