I'm just gonna throw this out there now to help your concept on this idea a bit. First off Stock doesn't work how you're explaining. If we were you implament stocks they would work like this.

TGS has 100 stocks total, I buy 1 stock for 500TC (This TC goes to TGS's bank account. Their rank goes up and their stock becomes worth 1,000TC, I sell their stock, another player buys the stock or TGS buys it back from me. I now have 1,000TC and TGS or a Player now owns that stock.

Now if I spent 500TC on a stock and their rank fell I wouldn't actually lose money per say. The stock would just become less valuable. Like the stock would drop to being worth 100TC. In the case of the stock going to like -100TC this does not mean I lost another 100TC it just means my stock is worth that little now. I would only lose the 500TC I invested in that stock if I sold it off.

Now in order to make clans become more competitive you have to come up with some system for the clan leaders to be able to decide and do certain things.

1. How much stock their clan will have. Also there should be a default starting price of each stock depending on how many the clan decides to make. To do this you would also need to set a base worth of each clan. for example since clans cost 25,000TC to make have that be the base worth.

Ex. I set the stock amount to 25 stocks, so each stock would be worth 1,000TC since a new clans base worth is 25,000TC.

2. Clans can't change the total amount of stocks they have in circulation without reclaiming all current stocks on the market. This would mean they would have to buy back all their stocks from other players in order to further divide them for more profit do to a larger base value of the clan than they started with.

3. Banned or Dead Players - It is an issue if a player gets banned or quits TB while in possesion of stock from a clan. In order to counter this you would need a system that doesn't exist in a real stock market. I would suggest something along the lines of a 6 month regular wipe of stocks. Once every 6 months return all the stocks to the clans and pay the players what they would have earned from selling their stocks at that time. If the stocks values were up you would gain, if they were down then you would just have lost the money you invested in that stock.

Thats basically more or less a more realistic approach to how this would actually work in TB and methods to troubleshoot problems that would come with it. Besides that I shit this idea if its handled properly.