I've built controlled rollouts, split tests and feature flags (all controllable from a dashboard) a few times now..
Any tips or tricks on how to productize an internal tool?
It's very early for me to give advice here, but I have just started productising an internal "tool" myself (https://officebots.io/), that I used extensively in my 1st bootstrapped startup, sold to our American competitor.
So while I am just starting, my approach is to think of myself as the "first user" (which I was), and define the messaging, user experience and target audience accordingly (eg I was the COO of a small company, and got a lot of value from the solution, so targeting now COOs of small companies).
Hope that helps a bit?