Having met [one of?] their prior CIOs, Tesla is infamous for a "build our own" strategy when it comes to their internal systems. They even built their own accounting system, a pretty commonly available application in the marketplace.
In regards to getting a HW3 replacement for FSD, don't hold your breath. That will only happen when FSD features require HW3 and aren't possible on HW2.5 hardware. No one knows when that will be the case, perhaps not even Tesla. If HW2.5 can run the FSD software then Tesla isn't going to upgrade a car to HW3. Now, in an infinite time horizon (thank you, John Siracusa) then you're going to get a hardware upgrade. When? Some day.