I saw this bike made by an independent bike shop for himself.
It's an electric longtail and can carry a 300kg europallet, plus the toolbox on the front, plus an extra person or material on the bike rack!
Here is the link to the shop website: https://www.cycles-penet.fr/
In the standard configuration the bike can already carry 200kg on the rack and the bike has a mechanical brake disk system, not hydraulic.
So with better hydraulic brakes and a slower speed (electric bike motors are limited to 250W in France so I don't think he will go very fast once fully loaded) the weight might not be too much.