Commercial users can get Pi's that you might never see as "in stock", the system works although we haven't tried it in that volume... . The supply issues for Pi's are the same as for the alternatives, and they should be easing. As you've probably noticed there are lots of alternatives that are stocked quite well, but none of them offer the raw compute you are after, often they do beat a Pi in one chosen metric such as connectivity or hardware decoding. The powerful alternatives are just as hard to buy, expensive and don't have those organised commercial channels that exist for the Pi.
If you have the requisite skills and time to design your own, then if you found a chip you thought looked viable you should be able to talk to the manufacturer or reginal disti about your plans and get a sensible price, I don't think this is any less risky than choosing a Pi CM4 tho'. Certainly they are quite happy to sell in pretty much any qty and depending on how exciting your project sounds, might have other help to offer.