I knew this guy in Cleveland that drove a classic GS750 (maybe a 20 year old bike). He used the clutch to get going, and then consistently shifted without a clutch.
The original GS series was overbuilt, and he could get away with this, but as Megadan states, the dogs on the gears will get worn down abnormally fast. It also hits the bearings on each side of the two shafts in the tranny harder every time you do it. This is especially significant with the inertia involved in a 4 cylinder engine, but not insignificant for the 169FMM ZS clone. You don't feel it, but the rpm of the crank is instantly changed (INERTIA). The dogs are the side links that connect input shaft to output shaft gears in the tranny. No clutch means they hit hard and the transmission controlling roller also gets shocked. Sure, you can shift without using the clutch. I remember getting really good at it. I thought I was clever
But I stopped and use the clutch all the time. No need to stress the transmission or the bearings on the transmission. It is up to you.
It sounds like the bike was abused pretty much already. Personally, I'd be careful with it, especially until I got used to it and assessed the damage.