I just came here to ask if anyone made some spreadsheet and here you are... That's helpful, thanks.
Also, after playing New Vegas, I thought - it also has DR & DT and different ammo types. And their system is very simple and somewhat easy to understand. I wonder why nobody tried to port it over to FO2? It still has 2 parameters that affect damage (DT subtract or multiplier and damage multiplier) instead of 1 (combined DR & dmg mult). The notable difference is that, in New Vegas, high DR armor is extremely rare and almost not used (without mods) and no ammo types have any DR mod.
After reading through the first post again, I still struggle to understand why the author felt so strongly about "juggling several stats". With just one value that controls the "penetration vs damage tradeoff", you are limited in how you can make different ammo calibers behave differently between ammo types. It an attempt to make the formula "simpler" than all others, I think it ends up still being a bit convoluted. The reason is that the game still has these separate stats (DR and DT), the fact that you don't like this level of complexity doesn't make them disappear (unless you hide them in UI or something). So the extra complexity of this formula comes from having this extra layer of indirection between one "penetration" parameter and actual DR & DT mechanics. YAAM has the same problem.
And the only way to not have this extra layer is to use all the modifiers separately (DR, DT, AC and DMG). You would still need to decide between multiplication and addition for DR and DT multipliers, but I think this would be the only true vanilla friendly way. Because, IMO, communicating how calculation works to the player is as important as achieving "good" damage numbers. Making decisions between weapon and ammo types is essential part of the gameplay. Maybe some players would just "has armor = AP, else = JHP" but I think it's interesting to actually look at stats of armor in game, look at what the enemy is wearing (they mostly wear stats based on armor, at least I tried to make sure of that in EcCo) and think if your weapon/ammo will work or not.
So I guess this approach might be worth pursuing, as I don't think anyone actually tried that. You can never have enough Ammo Mods in Fallout 2)))