Failover Design suggestion

Hi Guys,

I need to design a topology as below. Please help!

So basically I have a third party server (192.168.0.254/24) on the cloud and we will have to place our router inside their rack and they will provide two static routes. One active and one backup route and no dynamic protocols can be used. We need to access this subnet from all our centers (Branch Offices). How can I achieve failover (If one link goes down how can traffic be automatically switched to another path) with this setup as we are not allowed to use Dynamic routing with the third party and my firewall (Different Location)to this router is connected via point to point link (L2 Link). Please suggest.

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Note: Currently it's running on Point to Point IPsec VPN and we are in the process of changing that.