Hi,
If you follow some best practices you will never face any issue in this scenario.
Best practice is, bring up the controller which you want to bring up as a Master without connecting to the network. here you need to remove Master-ip from the local if you want to convert it to a Master. if you are happy with the L2 and L3 config, do not disturb any thing.
Now Apply Master-ip in the proposed Local Controller and it will reboot then look at the L2 and L3 config, if you are ok leave it
Now first join the Master to the network then Local 1 now ensure that the IPSec tunnel is up between Master and L1 and then Join the L2 to the network.
Here I'm assuming that you want to continue with the wireless config but you want to swap the controller roles.
Hope you got some more clarity on this.
Please feel free for any further help on this.