So when are you planing to release this addon?
When it is done.
I'm getting to the point where most of the easy stuff is done, now it's just endless testing and tweaking to make it all work together.
I've been trying different booster implementations, easiest way seems to be writing the whole vehicle as one unit, discarding stages as we go. However I'm leaning towards a more modular approach with attachment points so swapping the first stage is relatively straightforward.
The ULA document uses all the Atlas V and Delta IV launch vehicles, but I'm thinking of just building the Delta IV Heavy configuration. It can be used to launch all the spacecraft with plenty of fuel margin, and I like the idea of using LH2/LO2 for everything from first stage boosters to the spacecraft systems.
It is possible though to launch the Orion with a single Atlas V core and the heavier vehicles with a number of strap-on boosters, this would be the choice if your space agency is strapped for cash.