Have you tried adding 200 mods to Q3A and see how it perfoms? Really Morrowind is inefficiently written, not just the code but the data as well. So many small triangle batches and excessive texture switches in the nifs; performance improvements start with the artists' toolchain and good practices. There are still modders that don't include mipmaps or think they shouldn't use a full mipmap chain.
My Morrowind FPS is from an un-modded Morrowind. But basic Morrowind with 3 giant esms is like a massively modded game by itself. And I'm with you with mipmaps, it looks bad in the first place without going into performance benefits. And it is very hard to tell that to our talented texturers without sounding as a nitpicker.
CPU's have not advanced near as much as graphics cards, back when morrowind was launched, 10-15 million polygon's were about as much as a modern gfx card of the time could handle, with around 16 pipelines for shaders, and a cpu could be found running 1.2-1.5 ghz, now cpu's top out around 3-3.6 ghz(overclocking notwithstanding) regardless of the multi cpu systems and increased efficiency, they are around 300% faster than they were then, but gfx cards can handle 300 million+ polygon's per second and as many as 4-500 unified shader pipelines which are running more efficiently and faster than before, Quake was built around utilizing the gfx card, Morrowind was not, which is why morrowind only runs ~3 times as fast as it used to vs. quake....at least thats my hypothesis.
My theory is the same, my survey results clearly showing NO PERFORMANCE benefits from GPUs. All 2.8 Mhz rigs line around 70 FPS regardless of their GPUs. I should stop beating this dead horse now, I'm beginning to annoy myself. (Looking the roadmap's of Intel, their plan is to reboot from 1.8 with more cores every couple of years. They drop production lines for old ones and they sell high clock CPUs for ridiculously high prices like over $1000. (At least we have some engine reboots. I wish them success with all my heart.))