That will not work - if you set up multi gigabit WAN, the current Omnia’s CPU will be used to its maximum capacity (test–> Gigabit speed on WAN - PPPOE - #15 by zajdee, without sqm PPoE can deliver around 2/1 gigabit, with cake sqm 700/900 Mbit). As running heavy WiFi load will also eat a lot of CPU capabilities, this will decrease speeds even further.
So for this scenario you will need a more powerful device than TO (e.g. the advertised TO Enterprise).