How much freedom do we have to name players out of position (Soward at halfback, for instance, where he played when he first came to Saints)?
I'm glad you asked. Every position can play alternate positions in the sim:
Fullback: Wing or 5/8th
Winger: Fullback or centre
Centre: Wing or back row
Five Eighth: Halfback or lock
Halfback: 5/8th or hooker
Prop: Second row
Hooker: Halfback or lock
Second Row: Centre or prop
Lock: Hooker or 5/8th
There are also utilities in the game, but they're few and far between. At the outset of the season you can nominate a real life position for a player - so Soward could be a halfback or a five-eighth, for example.