Love how you implement bet sizing, this is a signature of professional traders. How did you come up with the idea?

You mentioned stocks are "seeded random draw", but professionals don't trade random stocks - there is no edge there, price movements are mostly noise. You want stocks-in-play, stocks with heightened interest from investors on that day.

My suggestion is to manually pick interesting stocks each day and ask players what happens next. Don't hide names, so that players can asses market strength and group strength - 75% of success comes from these factors, and only 25% from individual stock selection.