This would be a cheaper, lighter, more reliable but less drivable alternative to the already included manual transmission suitable for early utility vehicles.
I suggested something similar (and different clutch types) back in 2016, and the reply from the devs was that unsynchronized is not that common, and same as is side-head-valve systems, by the time you produce your first car in the Campaing, they’re already dated technology that won’t affect much the gameplay (or something along those lines)
Most things had synchro on all gears from the late 50s/early 60s and even in the 50s it was only usually 1st that went without. I think a lower driveability penalty on early transmissions could represent this in the game, or just maybe set the quality at -1 to represent it.
Only unsynchronized transmissions built in quantity in the time range would be ones for heavy duty trucks. It would make exporting cars to Beam.ng interesting if you were required to double clutch to avoid damage.