For the brown problem, I have no idea. I had this problem too, and it was the main reason I deleted it from my server.
There IS a datablock type called HoverVehicleData, which is designed to make stuff float a specific distance from the ground at all times.
Remember my hover carpet? It uses that datablock, and I'm pretty sure you could code it somehow to use the hoverboard model.
However, nobody has ever released a vehicle that uses that datablock, so it'd be a first for Blockland.
Finally, making an equippable vehicle like the skis isn't really possible without editing the player model. The ski model is a part of the player, in a weird way.
Although, you could look at the ski script if you just want the player to mount a vehicle from nowhere by using an item...