I want to build some wheels with some hubs I've got. The original rims were around 22mm in internal diameter running 28c tires. I'd like to get some skinnier rims about 15mm in diameter and run 25 or 23c tires. How much leeway does one usually have considering rim and hub length compatibility?

********************?? dont understand your question man. U want to use the same spokes or something?...

If you want to change the rim for something thinner just put another rim that is 700C clincher, just pick one in 700C and that match the holes u have in the hub, find ERD, buy new spokes, lace, done.

Agreed - and hub length?? The only thing affecting the tires is the rim, not the hub. If you are asking for what range of rim width would work for a given tire width see "Width Considerations" at this link: https://sheldonbrown.com/tire-sizing.html

I don't know of any bicycle rims that can't laced to any bicycle hubs, given that there are some similarities (spoke hole count).

I'd suggest you bone up on terminology/nomenclature a bit and it will make bit more sense. Ex.- there are no rims I'm aware of that have an "internal diameter of 22mm." LOL

If what you want to do is lace some narrower rims to your existing hubs, do it. You need to know some dimensions. One is the ERD of the rim- then the spoke circle dia. of the flanges- and the CL relative to the OLD. It's really quite simple to compile the parts... from there you're on your own.

Seriously- if you're building "a" wheel and you're confused, take it to the LBS.