You have a ton of options. Are you required to stay at 50cc? If not a 70cc kit would help alot with low end. I believe that you can get different transmission ratios for the rear hub as well.
what you really need is to tune your variator for a higher stall speed. Keeping your bike in the power range whilst on the low end gear of the cvt. That would help alot with the hills.
Wouldn't recommend it for street use, but you are in a unique situation.