Dual WAN on Diverge Circuit

Hi

We're new to Fortigate and we are testing our new Circuit with a 60E. 

We have a new redundant internet connection that share IP's. They are handed over through two juniper boxes. 

I want to configure WAN 1 and WAN 2 to work in fail over mode but I am struggling as both need to be able to run off the same IP's (not at the same time). So if Bell has a failure on a Circuit then it will automatically flip to the second circuit. All our IP's will move at the same time. 

Help! 

What I have done is create a virtual switch but I don't believe this is optimal. Thoughts? 

Running v5.6.3 

Thanks

Andrew