What about Aluminum-Air batteries?
Their power density is off the charts something like 1600wh/kg have already been developed. With the theoretical upper limit on energy density as high as 6000wh/kg.
The catch is they are not rechargeable.
But lets entertain a future where they reach the theoretically accepted maximum energy density, and start getting mass produced and efficiently mass recycled to the point it’s feasible to buy a new / refurbished battery for your paramotor.
At 6000wh/kg, the 20kg SP140 pack would hold an insane 120kwh.
Resulting in an insane 30 hours of flight time!
Even considering the 1600wh/kg figure that has already been produced. Such a battery for the SP140 would yield 8 hours flight time and put the ICE guys to shame.