If you want to do something along those lines I'd suggest that the Fund's starting money be determined by how much investing players put into it by buying shares. The manager would receive either a percentage of the Fund's profits or a fixed amount based on the number of shares bought. So the more players invest, the more money the manager has to work with. And the more successful the manager, the more players will invest and the more the manager's bonus upon delist. This could also introduce a new challenge for managers as the Fund's available, um, funds could decrease if players cash out after making whatever profit they were looking for. The one issue with this is determining when the fund would delist. Maybe all funds would have a set lifetime the way studio funds currently do. We'd also have to experiment with the maximum number of shares players could bur/invest in a fund.
(Hmmm, that gives me another idea. Limit players to investing X dollars and limit their maximum holding to 10? 50? 100? X dollars with any value over that being "cashed out" to the players portfolio as cash. So a player spends, say, the $100,000 maximum buying into Fund A. They are only allowed to hold $10,000,000 of Fund A, So on day 250 their investment reaches the $10m limit, on day 251 it goes up to $10,010,000. On reset at the end of day 251 $10,000 of their Fund A investment is cashed out. On day 252 their remaining $10m investment earns another $15,000 so the player gets another $15,000 in cash the next day. Have the Fund Manager get X% of those daily cashouts. However, programming this kind of Fund would take some work, I assume, and may be too radical or too much work for the management.)