Hovis's dream Burls Ti custom track

Chris King are less shouty in sotto voce, Cane Creek 110 might actually be better than CK. If you really want to go nuts, consider a big head tube and use the Cane Creek 110 with a conventional 1½" bottom cup and zero stack 1⅛" top cup (the blue one in the attached pic), then you can use a tapered fork like 3T Rigida, Easton EC90, Enve etc. You get the pleasing aesthetics of an integrated upper bearing and parallel sided head tube, backwards compatibility with a non-taper fork (by fitting a ZS lower bearing) and none of the imprecise fit associated with drop-in integrated bearings.

I specc'd a 1 1/2" headtube on my fat frame. Not many tapered fat forks around (fatback). But it seemed a good idea to future proof it. Getting a cannondale lefty for it now. Which will have a standard 1/8" steerer (as it has special clamps which are a touch longer). Will probably still go 1 1/2". But I feel the 1 1/8" with nice anodized external headset cups would look nicer.

My thinking was to get a pick'n'mix headset from Hope.

Can you get integrated Ti seatposts?

The top caps used with intergrated seatposts are widely available, and offer a cm or 2 adjustment. You simply spec the correct trube diameter for your seat tube.