That would be an awesome addition in future updates. I just didn't know if it was available currently. The more I work with building product bases in this software, the more I see things I didn't before that help us personalize it to our workflow which is deeply irregular to begin with so the concept that I had somehow overlooked the ability wasn't outlandish. Thanks for the help Matt!
You're not missing anything, there's no way to call ConfiguratorB from ConfiguratorA.
What it sounds like you have already figured out is that if you choose B, you can go down a different/additional route within A - that's the best way the product can handle what you're looking to do. But, again, you're right in that you've not got two bits to manage.
I think have a 'Add Configurator' button here, would do the trick.