In races where the boats at ghosts have an indicator. Where the other boats are "real" have a reminder announcement with the instructions. I crashed into someone and ruined their race thinking I would pass through.

Wind shifts and gusts would be good.Sailed in a snowstorm once and the pattern of snowflakes across the mainsail was an eye opener

Rain, gusts and waves

A dynamic Wave model that also shifts the boat off course

Be able to raise and lower sheets for when I want to dock or at least not cruise at the shore at 10 knots

Great application (!) The steering (tiller or wheel) seem to reverse from time to time and be counter-intuitive.

Courses feel too small, makes it hard to plot a decent lay line