Aren't stat increase by corpses already limited by potentials/hard caps? I've never been able to get much more Dx out of bug corpses than I can out of moss, even in 1.1.1. It's more efficient to do it with corpses, I guess, but then you've got to train your Wi back up, so you don't really gain there.
Speed is more of an issue, I suppose, since you can scum speed up to 150+ with bug corpses with some patience as long as you're strong enough to kill the bugs. Then again, you can do the same with quicklings once you're above level 25. It just takes longer.
Okay. So solutions.
1a. Make the cutoff for speed growth from bug corpses sharper. Reducing the potential gains to a maximum of 130 speed wouldn't be so bad.
1b. Make speed increases from corpses based on base speed rather than current speed (dunno if this is already the case in 1.2.0), so that you can't use slow monster/encumbrance exploitation/moloch armor to get more increases. This should really be done anyway even if the RFE is rejected otherwise, IMHO, for consistency's sake.
2. Make bug corpses (or speed increasing corpses more generally) have nastier side effects. Reduced lifespan, permanent decrease to PV, HP or PP, maybe?
3. Decrease bug corpse drop rate to the point where it just isn't productive to do this and leave everything else as-is.
4. Like bug corpses to a different stat. People would probably be much more squeamish about this if bug corpses were reducing the comparatively-hard-to-train St or Le.