At this stage for me, these are pretty obvious factors. Right now I am asking everyone about the exact gains and losses of delta V due to thrust and efficiency change over altitude but no one can give me a direct answer, so far the only answer I have from this site is the word "abstract", so I might as well find out myself.
Big boys like us already know that drag and gravity are the biggest contenders in delta V loss, efficiency/thrust gain on the other hand is still a mystery, and I am very close to getting my answer.
"if you won't let me buy a gun, I'll build one!"
I think that if you're going to make a catch all Dv system you're going to need to map air pressure from sea level to vacuum so you can work that against the drag co-eff of your launch vehicle.
Factor in weather effects on air pressure and density.
Then work out how that decrease in air pressure is going to affect either your ISP or thrust. As long as you have one you can work out the other.
Then you can figure out your TWR based upon fuel consp/weight and updated thrust value over time. That allows you to work out your theoretical acceleration against your drag value to work out the actual acceleration.
Then maybe (Altair can hammer me for this) factor in the changes in gravity as you get further from Earth. I know Dv only uses gravity as a constant so I'm not on about that but surely as gravity gets lower, the craft becomes 'lighter' and thus accelerates faster?
Then you'll have a continuously updated ISP for the continuously being updated Dv working alongside a continuously updated TWR for your drag model to fight against throughout your flight profile.
Or you've already worked it all out and I can just shut my dirty whorish mouth...