tl;dr tabis are basically Recklessness for your feet, and probably should stay that way
Tabis get you critically hit more often. That's not a tiny consideration. I'm not sure tabis need a nerf, given that they provide very minimal protection and increase the damage taken by the player.
Sure, probably a bunch of people wear tabis for the movement points, but a really good set of springs will give you more move points and move speed than tabis - mid-30s isn't unattainable, and I'm not sure you can get tabis that high without Skinner. So, really, people wear tabis because they either don't know how good boots are, or are simply content to play suboptimally.
Besides, if you want the bonus carry capacity of infused pig leather, you have to wear boots. Who doesn't want more carry weight, especially since it adds "smarter" than Pack Rathound? If you want the improved punchy crit of infused ancient rathound, you have to wear boots. And if you want to be immune to caltrops without spending a feat, you need metal boots.
I guess I just really don't think tabis need to be nerfed compared to boots (especially since infused siphoner tabis already got hit so hard), and your suggestion sounds like a direct nerf to tabis. I wouldn't mind seeing all boots give a +carry bonus as a competing bonus to the +move of tabis, though. Good boots that lace up over your ankles give palpable support all the way up into your knees (unless you're so young you don't notice that you have knees, in which case, enjoy it while it lasts) and make it much easier to carry a heavy pack on long walks.