I know this thread is pretty old now but I picked up a brand new G703 Hero for $90 AUD on ebay this week (RRP here is about $160 AUD) and today I had a go at some light modifications to reduce the weight.
The starting weight is 95g which is pretty good considering the original G703 was something like 107g. This just comes from the use of a smaller battery since the Hero sensor is very power efficient. The things I removed was the bottom magnetic plate, the inner power play magnets and cable and the huge battery cover. I also drilled some holes in the inner plastic shell since you can't see it from the outside, though I didn't go too crazy with it. The holes probably only reduced the weight by 1-2g.
While I had this mouse apart I noticed it has the Omron D2FC-F-K(50M) rather than the more tactile D2FC-F-7N(20M) found in the G403. Though the clicks still feel good enough that I didn't feel the need to change the switches.
Finally I used a small amount of strong double-sided tape to stick the battery down to a spot that helped keep the mouse balanced, and chucked on some Hyperglides. The end result is 87g with very good F/R weight distribution. I believe this is the same weight as the wired G403 without the cable. So that's pretty great for such an easy mod. I do own a paracorded G403 as well but now I don't really have a reason to use it anymore.
Something I noticed with my G403 is that if I took the magnetic cover for the extra weight out, the mouse felt front heavy. I think RJN points this out in his old review as well. Thanks to the placement of the battery in this mod that is not the case with my G703. The balance point is right in the middle of the sensor, which I think is ideal.
Primary System Specs: Lian Li PC-O11 DX - ROG Maximus XI Formula - Watercooled Intel 9900k (4.9Ghz) - Watercooled RTX 2080 Ti FE - G.Skill Trident Z RGB 3200Mhz CL16 32GB - Corsair RM1000i PSU - Samsung 970 EVO 2TB NVME SSD
Secondary System Specs: Fractal Design Define S2 - ROG Maximus X Code - Watercooled Intel 8700k (5Ghz) - Watercooled Strix GTX 1080Ti OC - G.Skill Trident Z RGB 3200Mhz CL16 16GB - Seasonic X-1050W PSU - Intel 600P NVME SSD