I have a huge Rocket espresso machine that I haven't used for 3-4 years, ever since I bought my Cafelat Robot. Honestly, I appreciate the engineering in this post but it's just not necessary given how good the Robot already is.
The manual control makes it possible to do flow profiling with something like a Timamore Nano scale, by adjusting pressure in real time according to the flow rate reading on the scale. I've been making and drinking espresso for a long time and nothing comes close to the flow-profiled spro I've made using this method.