I believe that this day and age we can get one connector that cover 80% of use cases. How I'd do it is have 1 4 pin barrel connector like the kind found on head

I believe that this day and age we can get one connector that cover 80% of use cases. How I'd do it is have 1 4 pin barrel connector like the kind found on head phones, I'd have 1 pin be ground, another be data, another be 3.3v, and another be either 12 or 24 volts. The 3.3v would cover lower power devices, 24v would cover higher power devices like stepper motors or servos. Technology marches on. Basically cheap powerful microcontrollers can act as a modem and do more complicated error correction, modulation, etc. I think you'd only get something like ~400 bytes per second, but that should be plenty for most hardware peripherals. You're not going to be doing hard real-time industrial control using this kind of system, but if you want to poll the air temperature, humidity, light level, and actuate a servo, once per second, you should be able to. For more complicated setups, like those where you pull a lot of amps or require hard real-time control, you may need to do things the old fashioned but you'll still be able to take advantage of other kitbash components. But it's about the abstraction, like if you need a precise motor controller (high amps, high speed sensing of current and rotation) you probably need something custom. Still, hopefully you can export a kitbash interface and all you need is a side-channel for the power. The cost is a $0.40 microcontroller on every device, which doubles the cost of many simple components, and it's not something I see being used in "properly designed" consumer products, but I think it would be entirely doable for the hobbyist/prototyping market. Imagine a bunch of physical hardware knobs, sliders, and buttons, and you can just wire them together to make your user interface.