where to start - well we all have been there. analysis paralysis... I still get it all the time but I find if I just put one foot in front of the other and start going in a direction... I'll immediately get a better sense of what I need to do!
for me... building always starts with design. Even if it's as simple as taking pictures of exhisting guitars and chopping them up into "my version"... it's good to have some sort of plan. for a dc body, altho I've never built one... I am keenly aware of the complications where the neck meets the body. Those necks are typically at an 1.5-4.5degree angle to give enough height at the saddles to fit a tom under. doing a neck through is sort of going to complicate... or simplify things depending on how you look at it. the center stock is going to have to be pretty thick to cut out a body and then an angled neck... if you get my drift.
so I would start there... you need to know what scale length you are doing (24.75 or 24.625 is pretty typical for a dc)... and what the saddle height is going to be at the intonation line. I would start by making a sideview drawing. doesn't have to be complex... just a 1/4" rectangle to illustrate the fretboard (maybe start out using fret2dfind to make a fretboard with your nut and saddle string widths... and given 24 frets let that dictate the length of your fretboard). make some little squares to sit on top of that and represent frets - at the height of the fret wire you intend to use. then draw a line to sit on top of those frets and run parallel to the fretboard... and make it the length of your intended scale length.
then maybe dig up a dc guitar plan (there are lots of them on the net) and measure the body length... now draw a rectangle to represent your side view of your body... with your intended thickness.
now draw a rectangle to represent your saddle height.
take the body and saddle and use a graphics program to rotate them to 1, 2, 3, and maybe 4 degrees... until the bridge/saddle fit under the string.
gibson headstock with a straight string pull... well the only one of those I am aware of is the flying v! it's not really possible to have the typical mustache headstock and still maintain straight pull. you could modify it... but it has to get thinner towards the top. I do however like that you started off trying to achieve the impossible!! (gibby headstock w straight string pull)
hope there is something above you can use!!