>>1963399>>90s roadbike, or mtb>>old school dirtbike barsPersonally i hate that look of quill adapters with 22.2 bmx stems. And I hate the look of moto bars. Usually they are also a huge weight penalty. An elegant setup uses a quill stem. It does not have to be expensive new stuff either, although if you plan to spec a dropper post and discs, i assume you plan to send it, and a nitto or otherwise reliable front end is not a bad idea.
>>1x8>>friction shifterI like friction but i don't see why you'd avoid indexing outside of specific circumstances, best is an indexed shifter with a friction mode. That gives the bombproof ongoing usability AND immediate utility. You very likely will get a nice -7 speed- wheel in which case you go 7 speed and if not then i don't understand why you'd be married to 8 either. 7,8,9,10,11 all make sense and you should be more flexible in planning and do what makes sense not follow some arbitrary vision which is nothing.
>>dropper post (unused left friction shifter used as lever)I don't actually think this will work well unless you put some serious effort into engineering it well. Much better to just use an actual dropper remote lever. There's also no reason to use an unused shifter which you can just remove instead. If it was an integrated shifter it would be different.
>>braze on disc brake mountPeak retardation. Lots of old mtbs are 1 1/8" quill and you can convert to a threadless disc fork and run a mullet setup instead but really why?
>>tubeless gravelkingsyeah? I have some 26" 2" gravelkangz i just got new. They ride reasonably well.
>>fendersDoesn't make an ounce of sense with your dropper post and disc brake ambition as proper fenders would be an extreme liability for trail riding or otherwise sending it. Zip tied coke bottle fenders can be mtb spec though.
>rear rack same as above, again, situational.
Your idea for a 'build' seems to be based on nothing, nothing more than a random assortment of memes.