I'd love to have your thoughts on the following topics:
1. It is very unpractical to wire everything on these in wall modules with 2.5mm² wire, so therefor my thoughts on how to make this more practical.
(Fibaro double in wall switch as example)

thick line would be 2.5mm²
thin line would be .25~.50mm²
all wires: 230V~
fuse on that loop is 16A
But is it technically (safety, fire, ...) and electrical (electricity certificate) - ok ?? (my country Belgium)
2. Is there anything else I should consider for the electricity certification when I install home automation (mainly in wall modules) (except the regular electrical stuff obvious) ??
Thx for reading, many thx for answering