How is performance affected in general by this?
Not at all .-) And I'm developing my Oolite related things on a 10 years old laptop with a weak CPU. It's still smooth and the FPS range doesn't change, so performance is not affected. The used framecallback doesn't do all updates in one turn though. On every call it just does one update. And the GPU is not in danger as well. It's 1 model with 12 subents (v 4 / f 2 for each). All are sharing the same shaders (~10 ALU), so shader-swapping seems to be no concern as well, but I'm using a pretty small set of AddOns while developing. Texture sizes are small as well (128px x 128px).
Sidenote: The more I think about it - a particle system could use the same approach. Maybe I'll do it next .-)
The only thing is the GC atm. I haven't looked at it closer yet, but I've seen an increase (not unexpected) when the map is active inflight.