If I would change body for a highly optimized one that will not lag like hell and don't try to kill my GPU with work of people that think SL is a rendering farm, of course I'll do!
This is what I'm doing too, I'm studying human topology for a long time, to get the best result with less polygons possible (and because I work with game dev in RL).
And not only body, clothes, hair, everything. A game character nowadays have between 15K to 40K, including clothes, hair, etc. Did you saw the amazing work in the last Lara Croft games? Her latest models don't have even half of the polygons SL models have (and I'm counting only the polygons in the first layer of SL mesh body, not the rest of the onion)
I know I'll receive some eggs in the face for what I'll say now:
Even with 100K polys a lot of models here looks like crap. I got once a male mesh body with 70K polys, and the elbow was bending like the arms of the old Disney animated movies, or, better, the game Cuphead, to have a good example. A crappy rubber arm with tons of polygons with loop cuts in the wrong places, while games can do an amazing elbow joint that bends like a proper elbow with much less polygons. And as Digit said, with things in the right places.
I stopped to buy clothes because I was getting high polys things with crappy rigging. Looks like people is lazy and wants to produce a lot. Just make the cloth in Marvelous, add details in ZBrush, throw an auto rigging in a 3D software, send this high poly to SL putting all other LODs to 0, and done. Good thing I usually walk away from crowds and end seeing just a single triangle of your amazing high detailed leather jacket with realistic zipper. Yes, retopology, baking and proper texturing can take days depending of the model, and needs a lot of creativity - and knowledge too - to get a perfect result with less. I just hope creators start to spend more time doing the right thing one day. It will not kill your creativity, as I saw in another topic months ago, it will make you even more creative.
Sometimes I walk around with wireframe rendering on, just to see how crazy the models are. And I just start saying to myself: "look, the triangles pattern from a mesh exported from Marvelous! Ewww!". Yes, I'm that crazy.
The lag and the low FPS will only diminish when creators finally understand and accept that SL isn't a rendering software, it works like a game engine (because it is technically a game engine). Rendering of realistic things with perfect light, good textures, no "pointy corners" thanks to a massive 100K polys body can take from some seconds to several minutes, even with the newest Eevee render from Blender (that is real-time). Who did it in any 3D software knows it. A game engine needs to render everything in the camera view (and a bit off-view too) in a speed of 60 frames per second, to get a smooth result. Now try to compress a realistic render that take seconds into a single frame that is 60/1 of a second. My GPU starts to scream only by thinking about it (and is not a crappy one, btw). And I'll not even start talking about hairs.
And yes, when BoM is released - and I hope they release it soon or I'll steal all LL donuts - , I'll release my "game ready" low mesh bodies too, humans, aliens, creatures, everything I do. My GPU will be glad. It's not the number of polygons that counts, is the knowledge. I prefer a low poly mesh body with a good work with the normal maps, proper rigging made in a proper topology, and a good work on texturing, instead of a 100K thing that will just cut my experience here, because I will need to put graphics low to not end with another fried GPU.
The picture I put here is one of my studies in topology. I still have a lot of work and refinement to do on it. Hope it don't go more than 20K tris (not polys, tris) when finished. Actually it has 5192.
My actual avatar is a little alien I did. And yes, I modeled the dragonborn clothes it wear from scratch, not just getting from the game. And, yes, I rip models from games, to see how they were done and learn with what was done, the tricks used to get a good optimization.
PS: it applies to everything, not only bodies. Even to that gacha animesh little cat a friend got and discovered it was eating 150 prims of her land.