So you bought a SC for the 99% of the driving you do. But want to change the suspension to cater to the 1% of driving you do. What? lol I am messing with you. But you have limited options at the moment. There are no aftermarket suspension parts that I have seen yet. It's too new of a vehicle with very limited production so far. Maybe next year we will see some options come out for springs and shocks.
I would suggest before you do anything to the SC, that you try lowering the tire pressure. That will give it a softer ride and offer more traction on rough off-road surfaces. See how that works out first. A/T tires will probably help as they are usually designed to flex more over obstacles. Especially when they have lower tire pressure as well.
If that isn't enough, try one of these?
The issue with the SC and a soft spring/shock rate is the limited suspension travel. You can't have it too soft otherwise it will bottom out a lot. Larger, true trucks, can get away with softer setups due to longer travel and typically a progressive bump stop. So even if you find something aftermarket, it won't come close to a true truck due to that limitation. Try the lower air pressures in the tires. I think you will be surprised by how effective that can be. Good luck.