You remind me of the Arduino connector standard, that includes a +5V power line and (traditionally) 5V logic levels. Often seen on FPGA based dev boards, where the main chip is NOT 5V tolerant.
0.1 inch style header connectors also tend to have clock speed limits.

So your “standard” needs to start by specifying a voltage level, and a maximum clock speed.
3.3-150 is 3.3V @ 150MHz, for example. You probably need an impedance spec as well, to avoid reflected signals on PCB traces.

When laying out something for generic use, consider the possibility of signals which could be useful but might not be used in every situation. What you’re making today might not provide an EN signal for the module, but if you provide an optional pin for it, and on the module can short Vin (or whatever) to that signal with a 0R (or the host project can have a trace doing the same) so that if it’s powered, it’s just enabled, but if you have a project where there’s a benefit to be had by controlling an EN pin, that can be facilitated.

Setting up breadboard friendly pin spacing and alignment certainly makes them friendlier to use by your friends who use breadboards (I largely avoid them due to capacitance and iffy connection reliability when using different gauge components). Obviously, if you have some pin headers coming out the top or side of a PCB, for connecting to through a header, those might not need to be aligned.

In a similar vein relative to module use for various projects, I have boards which sport multiple configuration options – two or three different regulation paths (Zener did you say? linear reg? switcher? bypass, expecting offboard regulation?), a couple of power inputs (barrel, pin header), etc. onboard PWM generation, or mcu provided PWM, or no PWM at all? This gives me options when I go to use the board. Of course, not all of the parts need to be populated. Creative tapered footprints allow for some parts to be different package sizes depending on what you have on hand. Parallel resistor pads allow for tuning a design (handy for current sense).

I have a mains switching board, originally designed with a MCU onboard when I made the home etch prototype (which itself is still in service). When I laid out the one for the PCB order, I routed all the MCU pins out to a no-populate row of TH for a pin header. Subsequently, I used a PCB without an MCU, instead connecting a small home-etch PCB with a comparator and external thermistor to control a fan in a decidedly more analog fashion (though I could have used an MCU and connected a thermistor to a power pin and an unused ADC pin). Designing some projects with an eye for using them for projects you didn’t have in mind when you did the initial design can be just as useful as them being a generic supply or driver. A little brainstorming up front can make the extra boards you get from some small PCB order serve other potential functions, or provide justification to order a lot more of some design.

Or olimex’s UEXT!

There’s an XKCD for this.

On my desk right now, I have I2C sensors that are pinned out VCC GND SCL SDA, VCC SCL SDA GND, … etc. Two of them (accidentally?) match.

https://hackaday.com/2022/05/04/the-connector-zoo-i2c-ecosystems/

https://hackaday.com/2016/11/09/my-life-in-the-connector-zoo/

I still like PMOD, but it’s soo big.

Also, put 0.1″ header holes over solderable jumper pads, enabling permanent or changable settings of the jumper.
Likewise, 0.1″ header pattern over USB connector pads; flexibility whether to use the connector.
Imagine the ways a module might be hacked, then overlay header holes there.

ultimately its a logistics problem. living in a small town in alaska i just cant get parts locally, and i am spending most of my hack money on shipping. so when it comes to buying a hundred different parts from 10 different stores, or buying a few knockoff dev boards from china (sometimes sparkfun or adafruit but they are overpriced, and the latter has horrible shipping terms to ak), gluing dev boards together wins out.