Worse combustion chamber design ever? Saveable?

Yup but at least those had the benefit of the slanted deck so it was arguably better and still pretty much a wedge chamber. The Jags were "straight" so the only place for the mixture to go was a bowl in the piston and even with quench that just doesn't work well in spark-ignited engines.
Yep and crower made the pistons for them so they could even be competitive .