I'd like to flight plan a bit higher than 10,000 feet but the VFR planner (which seems to be the most relevant for flight planning) only shows up to 10,000ft which is odd because the meteorgram forecast and IFR pages show higher. Mainly for clouds/freezing layers and winds aloft though the VFR page is most helpful. Edit: VFR flight is legal up to 17,999 ft so that would be a great maximum for that page in my opinion.

For an extreme example, lets say im flying out of Aspen CO, the VFR page is literally useless.

Other helpful additions would be the ability to add your planned flight level in addition to airspeed (I know thats already there, but I don't think it calculates for winds) so it could more easily forecast your arrival time and weathers.