Yes I'm thinking about the best way to render the exhaust. Proton has a very distinct "underexpanded" exhaust at launch, a bit too much coherent to be simulated by particles. An old-fashioned texture that fades and expands with altitude (Velcro Rockets did that I remember) is always an option, but I'm wondering if some transparent AND emissive 3D model could work. It could scale up (animation) and fade (alpha level) to simulate overexpansion.
Or, if that proves impossible, I still could use that model to make a screenshot and a clean flame texture.
Then there's a contrail of turbulent hot gases, that's easier to do. LC 81/23 or other Proton pads have two big trenches on the sides that generates those "volcanic" gases bursts upwards. That was nicely done in Thorton's addon, so I think that part, with a lot of testing and fine tuning, will be possible. At some point I'll have to code a "vessel-launchpad" to manage all the ground stuff anyways.
Right now I'm using stock Atlantis SSME exhaust, its not that far from the truth.
That one is crazy, I think the rocket casts shadow on its own exhaust. Amazing :