I also produced S-A-A V2.2 with KICAD in my spare time recently, adding an amplifier to the reflection signal path--TRF37D73, and replacing the mixer with LT5560(So far it seems to be the wrong choice,because it needs to add a balun).
A redesign of the reflection bridge could lower cost (e.g. MMIC based differential amplifiers instead of 2 baluns) and/or improve SNR which can allow faster sweep rates. etc etc.
---It look like this£¿--
I plan to re-submit a new version.
