[8.300] Multi path rules, unable to select 3g/UMTS

Hi all
I'm a bit stumped.
When the main WAN link has failed I want Astaro ASG to Failover to 3g/umts with only a select rule set with QOS to limit what is downloaded/accessed.

Setting up the Failover under Interfaces/Uplink balancing is easy.

But what is the best way to achieve the selective rule set?
Rule set = SMTP, HTTP (with no file downloads), HTTPS.
I can set up a Group with the above, and a QOS group.
And add another Nat Group.

But there has to be a better way?

When I look at the Multipath rules the only option available is the WAN link.

Thanks

Mark