Just to give an update. I have done all of your advice.Our main ISP is now working on both Meraki and client. I just have concern with my failover.
Original set-up : ISP->Meraki->Client
New setup : ISP-> L3 Switch -> Meraki and Client.
On the original set-up,my failover is connected to WAN2 port of Meraki. Please note that my failover is working perfectly with Meraki. When main ISP(WAN1) is down, WAN2 will take over until WAN1 is up again.
On the new set-up, I configured a Layer 3 switch and connect both the client and Meraki in there.
So now, instead of my WAN2(failover) directly connected to Meraki port.
I connected WAN2 to our Layer 3 switch first. Then from L3 I connected it again to WAN2 port of Meraki. I tried to unplug WAN1 from Meraki, WAN2 take over as usual but when I put back WAN1 and perform traceroute I notice that it is still the WAN2 on the route. It should be WAN1 again. What should I configure in Meraki?
Please also note that the L3 switch does not have the capability to do failover that is why I am counting on Meraki and client to configure the failover.