Wireguard client with multiple failover wans

Installing and Using OpenWrt Network and Wireless Configuration
1

I've configured OpenWrt router as wireguard client and the router has multiple wans. I want the wan used by the wireguard vpn to failover to multiple wans available.
Below are my configurations

/etc/config/network

config interface 'wan_0'
    option  ifname  'eth1'
    option  proto  'dhcp'
    option  disabled  '0'
    list  dns  '8.8.8.8'
    list  dns  '1.1.1.1'
    option  peerdns  '0'
    option  metric  '10'


config interface 'wan_7'
    option  ifname  'eth3'
    option  proto  'dhcp'
    option  disabled  '0'
    option  metric  '5'


config interface 'wan_8'
    option  ifname  'eth2'
    option  proto  'dhcp'
    option  disabled  '0'
    option  metric  '60'

config interface 'wg_1'
    option  proto  'wireguard'
    option  private_key  'pppppkkkkkkk'
    list  addresses  '10.1.2.2/24'
    option  mtu  '1420'


config wireguard_wg_1 'wgserver'
    option  public_key  'pppppkkkk'
    option  endpoint_host  'some_host.com'
    option  endpoint_port  '2900'
    option  route_allowed_ips  '0'
    option  persistent_keepalive  '25'
    list  allowed_ips  '0.0.0.0/0'

/etc/config/firewall

config zone 'wan_0'
    option  name  'wan_0'
    option  network  'wan_0'
    option  input  'DROP'
    option  output  'ACCEPT'
    option  forward  'DROP'
    option  masq  '1'
    option  mtu_fix  '1'

config zone 'wan_7'
    option  name  'wan_7'
    option  network  'wan_7'
    option  input  'DROP'
    option  output  'ACCEPT'
    option  forward  'DROP'
    option  masq  '1'
    option  mtu_fix  '1'


config zone 'wan_8'
    option  name  'wan_8'
    option  network  'wan_8'
    option  input  'DROP'
    option  output  'ACCEPT'
    option  forward  'DROP'
    option  masq  '1'
    option  mtu_fix  '1'


config zone 'wan_zone'
    option  name  'wans'
    option  input  'DROP'
    option  output  'ACCEPT'
    option  forward  'DROP'
    option  masq  '1'
    list  network  'wan_0'
    list  network  'wan_7'
    list  network  'wan_8'


config zone 'wg_1'
    option  name  'wg_1'
    option  network  'wg_1'
    option  input  'ACCEPT'
    option  output  'ACCEPT'
    option  forward  'ACCEPT'
    option  masq  '0'
    option  mtu_fix  '1'

/etc/config/mwan3

config interface 'wan_0'
    option  enabled  '1'
    list  track_ip  '8.8.8.8'

config interface 'wan_7'
    option  enabled  '1'
    list  track_ip  '8.8.8.8'

config interface 'wan_8'
    option  enabled  '1'
    list  track_ip  '8.8.8.8'

config member 'wan_7_m'
    option  interface  'wan_7'
    option  metric  '10'
    option  weight  '100'


config member 'wan_0_m'
    option  interface  'wan_0'
    option  metric  '20'
    option  weight  '100'


config member 'wan_8_m'
    option  interface  'wan_8'
    option  metric  '30'
    option  weight  '100'


config policy 'wan_policy'
    list  use_member  'wan_7_m'
    list  use_member  'wan_0_m'
    list  use_member  'wan_8_m'
    option  last_resort  'blackhole'


config policy 'drop_traffic'
    option  last_resort  'blackhole'


config rule 'vpn_all'
    option  src_ip  '10.1.2.0/24'
    option  dest_ip  '0.0.0.0/0'
    option  use_policy  'wan_policy'

I want my vpn traffic to failover over wan_7, wan_0 and wan_8. what I'm doing wrong? How this can be achieved?