Hi Sebastian,
The variable 'P_ref' is equivalent to the "Reference output electric power at design condition" input on the Power Cycle page for the Molten Salt Linear Fresnel model. I think you should change that variable instead of 'system_capacity'.
The weekday and weekend schedules won't have an effect on the results if you don't also change the dispatch control inputs (see the Thermal Storage page in SAM to see what I mean). Those inputs have names like 'tslogic_a', 'tslogic_b', 'tslogic_c', and 'ffrac'. I recommend using the SAM code generator to see those variables in the JSON file as described here:
nrel-pysam.readthedocs.io/en/main/inputs-from-sam.html
Best regards,
Paul.