You have my attention.
Every technology seems to have its own downfalls...
BLTouch - Poor (but "good enough") accuracy.
Inductive - Needs a specific build plate material and has trouble with thicker glass plates or aluminum beds.
Capacitive - Thrown off by too many outside influences.
Servo+Microswitch - Bulky, fiddly, too much mechanical slop for accuracy
IR - Trouble with transparent or second-surface reflective surfaces
Piezo carriage - Thrown off by plastic buildup on nozzle and requires mechanical slop in the carriage to operate
Acoustic contact - Complicated and costly as a result.
Sheet of paper - Slow and tedious.
Looking forward to hearing what you have in the works.