Quesiton: Leased Line Issues. Need Alternative.

Hi, I have this client in China using Fortigate 60D. they're issue now is that they have high bandwidth usage on wan2 (leased line to HQ) so means their HQ is giving internet to this branch. For wan1 is their ISP. The issue with their ISP is that they blocked google. But my client is using google based email so that's why they have to use wan2 to access google services.

My past engineer did using policy routing. primary is wan2, and secondary is wan1.

So right now, everything will go to wan2 even google websites using wan2.

The max bandwidth for their leased line(wan2) is only 10Mbps, so naturally if they have a lot of updates, will be high usage.

#Question, how do I let only google services or their servers to pass thru wan2, and other websites will be using wan1?

I understand it seems SD-WAN is the only way. But the problem then I have is that the leased line I need to disable the NAT.

Need help from all the professionals here.

Thanks.

Regards,

Hazmi