A little delayed. I posted then left internet access for awhile.
I have not modified a KR804. I assume it’s possible to adjust the dial to work within a different grinding range, not sure by how much.
I would not use KR804 for espresso, because regardless of this singular study showing superior uniform particle size, ease of use is a real concern; for us it works well for everything else. The vibrator plate is intended to distribute grounds in a bag you would be grinding into, but sounds problematic for dosing into a portafilter even with a dosing ring.
Lots of grinders fit well within your considerations but there are a lot more things to think about. Espresso volume? Will you batch brew? Do you want to grind coarsely for french press? Do you want to grind in bulk for cold brew? How many origin options do you want on espresso at a time? Is barista ease of use a concern? For instance unless you intend on having a low volume cafe, I would lean towards using a grinder designed for espresso on an espresso bar. Lots of reasons for that.
For instance, a random thought, for uniform particle size, a recent grinder development has been a cooling system within an espresso grinder. Socratic’s experiment does not take heat into account in the graph above. After thirty minutes of consistent use, a Peak or Mythos grinder may easily end up more consistent than an EK43 or Ditting because of this system. Lots more to think about.