I would think that all the smiths you mentioned will build one hell of a gun ! Obviously there are alot of guys on the LRF with personal experience dealing with Shawn and Kirby. Both are great guys and go the extra mile to give their customer what they want in a gun.
From my one personal experience having a custom job done, I can say that dealing with Shawn Carlock was a fantastic experience. I ended up recieving a complete system that in good conditions will put 3 shots into a tennis ball at 800 yards. I now have several 4 and 5 shot groups at 1030 yards in the 4 " range. The calibre I chose was the 338 edge. It is setup very similar to the lightweight package he offers as std. sedero taper Hart 30 ".
Having an accuracy guarantee is the reason to get one of these guys to build it ! No faulse promises. It will do what they said it would or it does not leave the shop till it does.
As far as time frame to get built, I'd think you would be looking at 9-12 months from all the names you mentioned. Top gunsmiths are busy people.
You are certainly on the right track. Buy right the first time and you will be a happy man !
Good luck my friend !
With each step in the bush, you are a step closer.