[dfxm12]

I don't think any of these issues are solved by selling you a pile of parts and having you build the machine yourself. An open/more flexible PID is a great idea, but that's just one piece of this product & could be built into an already assembled machine. There are some machines (Decent, Sam Remo You) that give you a lot more control, but even this level of control probably goes unused by a lot of its users if the h-b forums are to be believed.

More control than that, or a totally open PID, might be a hard sell for safety reasons. That alone is a nonstarter, but even as you approach that level of openness, it would be pretty hard to support and really isn't needed if you just want a good shot of espresso and aren't taking an niche academic approach to an already niche process. This is why you likely won't see it in more commercial machines.