I do not think there is a way to do exactly what you want in an automated way, however you could make use of the group based bandwidth management features to have the config in place that could be easily turned on if the primary WAN was down for an extended period.
Peplink has a system that allows you to place devices into one of three groups, each group can have a per user bandwidth limit and then a reservation of the overall connection per group.
Groups are defined as Manager / Staff / Guest.
My approach here would be to statically assign IPs to the TVs and cameras and then add those IPs to each group.
In the example here I have two IPs 192.0.2.1 and 192.0.2.2 - they have been assigned each to a different group.
You have to repeat this for each IP, or make use of the built in “All DHCP reservation clients” group which could for instance be used for all the TVs if you assigned them IPs for DHCP reservation. If you have different VLANs in use you could also match against the subnet that each type of device is in.
Once you have added all of the devices you can then specify a per-user (per-device) bandwidth limit, you would have to just turn this on/off as required but would get you the end result you are looking for.
As an aside this is one area of the Peplink products that I find the most limiting to work with and could really do with some enhancements:
Add a feature to allow comments on against the IPs / subnets so you know what they are meant to be!
Add the ability to define more than the built in “Manager, Staff, Guest” groups.
Add the ability to use grouped networks instead of just single IPs / subnets (this would need some thought as to how rules are then processed, like you allow arbitrary sorting for outbound policy) as it would make managing larger groups of devices easier where you cannot resort to using specific subnet matching.
Add exactly what the OP here is asking for, either a config for per-user bandwidth limits per wan, or another way would be to allow us to reference a traffic shaping policy against an outbound policy rule, so for example when traffic is being sent via a specific WAN users are able to be restricted.
Change “DHCP reservations” group so you could for example say “all dhcp reservations from this subnet” to allow greater flexibility in how that is used - e.g. I want all the reserved IPs in this VLAN to be grouped as “Guest” but all the DHCP reservations from another VLAN to be treated as “Staff”
