I would add the ability to create corporations, hedgefunds and shareholder agreements. I would also add more utilities and infrastucture. Airports, deepsea ports, highways, telecommunications, and even garbage disposal are some ideas. These could all be purchased. Combined with the ability to create hedgefunds, corporations and shareholder agreements, you could pool capital, borrow capital and purchase more expensive property or developments. By allowing for shareholder agreements, you could also share revenue by percentage owned in a company.

Also, I would privitize the bank and allow for more liberal borrowing. This of course would be coupled with higher interest rates and the ability of the bank to freeze / seize assets on loan defaults. Players may purchase shares in the bank and receive dividends from interest earned.

The pieces and paper money.

Jimmy