
Start:
3 categories: Boarders, Skiers and half-cross.
The boaders start first, then the skiers start, trying to catch up with the boarders who will try to keep the lead. After all the adrenaline pumps have left the starting line, the half-course crossers will have a more chill start and a nice crossing without worrying about being in the way.
In each category, all participants start at the same time. The start line can be long for safety reasons, but it is equalized by a turn around point straight downwind. You can choose the straight line (slow but short) or the angle (fast but long).
Turn points:
The first downwind turn point will space the riders a bit. Then they have to head upwind, and plan strategically how they will tack up.
After the turn point, they head slightly downwind for a sprint to the finish line.
The half-course upwind mark can be set cross-wind with the finish line to make an easier crossing.
The turn points can be made of single line kites anchored with long colorful tails and such as this one:

They can be anchored down with an ice-screw.
Thoughts?