Route Site-to-site traffic from (Remote Office A) through (Remote Office B) to Head Office

Good Day,

We have 2 remote offices with a site-to-site link connecting to Head office.

Network config for offices:

• Head office: 10.x.x.x/16
• Remote Office A: 172.16.x.x/16
• Remote Office B: 172.17.x.x /17

Have fail-over links connecting both remote offices to head office and all working as expected. 

Trying to route traffic from Remote Office B through remote office A to Head office incase the link between Head office and Remote Office B fails unexpectedly. 

This is to ensure that any site has random port flapping the traffic will still route to head office.

Will this solution work or does anyone have any other solution? support.sophos.com/.../KBA-000009448