Switched 12V supply

Hi,
to simplify my wiring i think about useing a switched 12V for the emu power supply. In OEM wiring i have a “small” KL30 wire with 0,5mm², which is probably not enough to supply the whole emu, but 3 “big” supply line comeing from a power relay.
The supply will be coupled to KL15…means all power line are turned on and off with KL15. Its written in the manual that this is possible, but are there any downsides useing it like that?
And are all the 12V supplies of the EMU internally connected or is it probably possible to connect some to KL30 and some others to a relay supply without supplying each other?