Christian,
While I'm also still a noob to the Optimizer,
I'm pretty sure that you are correct. Just like if you were to use two different types of pellets or weights,
you'd have different points of impacts, thus having to account [zero] for each of them.
The said deal would apply for swapping a scope / Optimizer combo around on multiple rifles [different rails / MOA angles]
I actually thought about that since I tend to shoot a few different rounds..
Indoors, I almost always shoot Crosman Premier 14.3g HPs
Outdoor, I'll shoot either JSB 18s, or, H&N 21s [For longer distance / more stability]
Is there a possible work around? I think so..
If you're going to be using 2 different pellets, split the the tape down the center..
Mark which pellets you'll be using: 1 = left side of the tape 2 = right side of the tape.
Then just mark as you would normally, but, do it twice. [so you'll have yard marks for each pellet type/weight]
I don't think that the wheel or tape is wide enough to do 3 different pellets, but I'm sure that can be modded too.

Sam -