I have a 2013 Giant Roam 2 which I use for winter commuting and Chariot towing. I feel like I'm outgrowing it too in the same way (feels sluggish commuting vs my road bike). Based on a bit of research, swapping out the suspension fork for a carbon fork would save about 4 lbs (I've contemplated getting a China carbon fork off ebay for about $100). Personally, I don't think there's much gain to be had without switching to more aero geometry, as weight really only slows you down accelerating and going uphill.
I'll probably replace my Roam with a cyclocross bike if I can find something with granny gearing to pull 50lbs of Chariot and toddler uphill.