I did some experimenting on a WRT1900AC V1 since the LAN Marvell Switch Marvell 88E6172 is very similar to the WRT3200ACM LAN Switch Marvell 88E6352 (same port numbers etc.)
I am focusing on the LAN LEDs as I seem to be able to set the other LEDs via LUCI LED Configuration page.
I tried your recommendation to add a switch command in the network config file (/etc/config/network) but I tried a lot of combinations and no effect at all. I added the following in the config file:
config switch_port option device 'switch0' option port '3' option led '0'
According to the switch setup Port 3 is LAN 1 on the router but I tried Port 1 to Port 6, restarted the network on each change and no effect at all on the LAN LED.
I then tried another logic and left it on Port 3 and changed "option led" from 0 to 10 and restarted the network on each change. Still no effect at all.
Does anyone have any ideas on what else i should try to control the LAN LEDs on a WRT3200ACM or WRT1900AC V1?