This is a tremendously entertaining time waster. I think some of the folks griping about bugs and such folks could benefit from a little perspective - this isn't your job and you aren't spending real money on it. It's a game where you occasionally click the mouse and watch numbers go up - just have fun!
I'm thinking an "investment manager" would be interesting. Pay a upgrade fee to get it, then a transaction fee and/or a percentage of the investment and then the investment manager will purchase additional businesses for you without you having to click. Depending on how detailed you wanted to make it you could have a rules setting so you can tell it how to invest. Or you could be able to pick only one business type (lemonade stand, whatever) that your investment manager will automatically purchase as the funds become available in your account. Haven't fully thought it through but it would be an interesting feature set to consider.
 "AdVenture Capitalist"){kind=icon}
 "Idle Mine"){kind=icon}
 "Clear Vision 5"){kind=icon}
 "World Rebellion II"){kind=icon}
 "experimantal project- try it out"){kind=icon}
 "IntoSpace!"){kind=icon}