The seat itself is comfortable for just casual riding on roads but when you are on a trail the seat has zero side to side support, any options to resolve this maybe with arm rests?

None that I know of, maybe someone has come up with something on their own and will reply.  I've only had a passenger for mild trail riding, nothing crazy and the passengers thought it was pretty comfortable. 

My wife and I have ridden some more advanced stuff and I guess the best way to put it is that the passenger has to be an active participant.  She likes the seat and has never said to me that she feels that she could slip out or what have you. But again after a good ride the next day her arms and legs are sore... like she had a workout.
I don't know of any product that can be used to create a more secure seat other than riding responsibly. No judgement just an observation is all.
sol...

[2015 Z Force 800 53/Trail EPS]

Reviews I have seen say the CFM 2-up seat is one of the most comfortable out there. They even compare it to the CanAm. I think we also have to keep in mind that the passenger is an active participant in the ride and has to be able to adjust as needed...as well as be able to bail-off in a rollover. Wouldn't want something that would effect those functions...IMO.