+1 on Lightwave is amazing for fretless.
I can't imagine it being anything but "clacky" & too bright on a fretted instrument. But plenty of people do it.
I have one of the original Zon Sonus Fretless 5s with the earliest version of the Lightwave S1 system. It has not been without its problems, but when it is working it is amazing. Mine has been out of commission (one of the pickups failed a few years back & I've just been too busy to do anything aout it), but with excellent customer service from Lightwave, I'm getting it working again.
I've always used some, but very little of the piezo. The instrument sounds sterile & flat if you leave it totally off, but more than just a tiny bit of it and it starts to sound real bright & weird and can even feed back if your amp is up loud & you get your bridge too close to the horn in your cab.... (again, this is from the earliest prototype of the lightwave system, the piezo may be voiced differently now. there is also a control on the preamp board having something to do with the piezo... maybe a highpass frequency? i forget. some EQ setting, anyway)
I am very excited to play this instrument again. I played nothing but my fretless zon from 1999 till about 2005. The broken pickup coincided with my re-discovery of the fretted bass, and I've been playing nothing but fretted since.
Anyway, great system, glad they are still around & very pleased with their fantastic customer support. I (somehow, unwittingly) got a bass with a prototype of their earliest system from 10+ years ago, and they still offer no questions asked top notch customer service to me. That is awesome.