You could force certain services, say HTTP, HTTP, SMTP, FTP etc. to go out WAN2 and thus leave WAN available for gamers, by setting specific LAN firewall rules to use specific WAN2 gateway under advanced –> Gateway options on each firewall rule for certain services.
I know it's not exactly what you are looking for, but, it will help.
You could take it one step further and create 2 gateway groups WANgamers with WANgw in it Tier 1 and WAN2gw in it Tier2 and a second gateway group called say WANgeneral with WAN2gw in it Tier 1 and WANgw in Tier 2.
That way, each Gateway Group will have redundancy and failover to the other WAN, but, prefer to use a different WAN gateway normally.
Then, your firewall rules will ALWAYS reference a specific gateway group, either WANgamers (which prefers to use WAN) or the WANgeneral gateway group which prefers to use WAN2.
I hope that helps.