Re: buy a sendero or have a gun built??
IMHO, start with the Sendero, if that is close to what you want.
I began with a Remington 700 LH in 270 in 1982. It got a Garrett glass stock in 1990, a Jewell trigger in 2000, a Shilen barrel in 2004. And it is now blueprinted with an alloy bolt shroud,etc.
It is now 6.5 lbs ready to go with a Leupold compact, unbelievely accurate and darned pretty as well.
Total cost...$2k spread out over years.
The out of the box Remington Sendero is 90% of what you want. And that's 150% of what you really need to hunt, and enjoy it, accurately, at good ranges.