Dale, you have a very good valid point that deserver consideration, and some study.
I have read and search FAR's and cannot find where it says I can install a non TSO' d part, but I also cannot find where it says I cannot install a non TSO 'd part.
My reasoning is that In order to install the part as a Minor Alteration, I (the A&P installer) am responsible to determine that the part is not a major change to the TC, and that it can not have any effect on the operation or performance of the aircraft and does not interfere in any way with any other modification.
The part, SkySensor is the exact same part (except a mirror image) of an approved TSO' d and STC' d part with several electronic components left out, and ADS-B IN electronics installed.
I believe that it meets those criteria, and actually contributes to Safety of flight.
Unless I find an FAR that says why I cannot install it as a minor alteration I feel comfortable doing so.
Any A&P must make there own evaluation.
More thoughts on the subject are encouraged.
Bill B