Why not just add the third WAN to your failover such that it only is used when WAN1 and WAN are down......... seems like a huge over complication??
here please check my Config sir.
i have 2 stations
my 1st station has 2isp which i use as wan1 and wan2.
my 2nd station has only 1 my other isp which have big loads of traffic.
but then sometimes my 1st station wan1 and wan2 goes down so i use my 2nd station as for wan3 for emergency backup connection.
i am using pcc load balancing on my 1st station and adjusted for my third wan.
3\0 wan1
3\1 wan2
3\2 wan3
and i placed routing marks for each wan routes.
/ip route
add check-gateway=ping distance=1 gateway=192.168.10.1 routing-mark=wan1-mark
add check-gateway=ping distance=1 gateway=192.168.11.1 routing-mark=wan2-mark
add check-gateway=ping disabled=yes distance=1 gateway=192.168.12.1 routing-mark=wan3-mark
add comment=WAN1 distance=1 gateway=192.168.10.1
add comment=WAN2 distance=2 gateway=192.168.11.1
add comment=WAN3 disabled=yes distance=3 gateway=192.168.12.1
when my wan1 and wan2 is up i disabled my wan3 routing mark to prevents packets.
i am using netwatch for better failover ping:
/ip route
add check-gateway=ping comment="Netwatch WAN3" distance=1 dst-address=\
8.8.8.8/32 gateway=192.168.12.1
add check-gateway=ping comment="Netwatch WAN2" distance=1 dst-address=\
8.8.4.4/32 gateway=192.168.11.1
add check-gateway=ping comment="Netwatch WAN3" distance=1 dst-address=\
1.1.1.1/32 gateway=192.168.10.1
/tool netwatch
add comment="Failover WAN1" down-script=":log warning \"wan1 timeout\";\r\
\n/ip route disable [find comment=WAN1]\r\
\n/ip route disable [find routing-mark=\"wan1-mark\"]\r\
\n/ip route enable [find comment=WAN3]\r\
\n/ip route enable [find routing-mark=\"wan3-mark\"]\r\
\n" host=8.8.8.8 interval=10s up-script=":log warning \"wan1 is up\";\r\
\n/ip route enable [find comment=WAN1]\r\
\n/ip route enable [find routing-mark=\wan1-mark\"]\r\
\n/ip route disable [find comment=WAN3]\r\
\n/ip route disable [find routing-mark=\"wan3-mark\"]\r\
\n"
add comment="Failover WAN2" down-script=":log warning \"wan2 timeout\";\r\
\n/ip route disable [find comment=WAN2]\r\
\n/ip route disable [find routing-mark=\"wan2-mark\"]\r\
\n/ip route enable [find comment=WAN3]\r\
\n/ip route enable [find routing-mark=\"wan3-mark\"]\r\
\n" host=8.8.4.4 interval=10s up-script=":log warning \"isp2 is up\";\r\
\n/ip route enable [find comment=WAN2]\r\
\n/ip route enable [find routing-mark=\"wan2-mark\"]\r\
\n/ip route disable [find comment=WAN3]\r\
\n/ip route disable [find routing-mark=\"wan3-mark\"]\r\
\n\r\
\n\r\
\n"
add comment="Check WAN3" down-script=":log warning \"wan3 timeout\";\r\
\n/ip route disable [find comment=WAN3]\r\
\n/ip route disable [find routing-mark=\"wan3-mark\"]\r\
\n" host=8.8.4.4 interval=10s up-script=":log warning \"isp3 is up\";\r\
\n/ip route enable [find comment=WAN3]\r\
\n/ip route enable [find routing-mark=\"wan3-mark\"]\r\
\n\r\
\n"
i wanted to enable my 3rd wan and its routingmark only whenever my 2 isp goes down. and maybe it only goes for script.