My tinkering with such things made me think it's not necessarily worth the hassle. To be sonically noticeable, the changes often require extreme positions, working like on/off switches. When conversely there's a resistive sweet spot to find, pots are often too touchy to give the right resistance, that a switchable resistor with a fixed value would deliver on request.
Also, if a blender is grounded, it lowers the overall resistive load, making the sound duller and forcing to compensate with other solutions (1M and/or no-load pots, typically).
I've still a few instruments with such controls because they avoid to drill new holes. Blenders are also handy when there's not enough space for a push-pull pot. But I rarely set any blender somewhere between 0 and 10 - except for blending a bit of neck pickup sound in parallel with the bridge one, and/or with out of phase pickups.
YMMV. Just sharing my own subjective experience, FWIW.