Is there any way (an extension, plugin, etc) to buy whole companies in multiplayer mode in openttd? Doing a fusion of companies would be quite an interesting challenge.
First, in order to enable buying shares, the server needs to have the relevant 'Competitors' option set (allow buying shares).
According to the openTTD wiki, even with this option on it is impossible to buy more than 75% of the shares from non-AI opponents or buy any shares at all from companies that are less than 6 years old.
Completely buying out a human opponent in multiplayer is disabled because code to transfer a client to another company server-side does not exist. You would have to patch the code for openTTD to gain this functionality. See also this topic.
In the original openTTD, your loan would be added to your company value. Two human players could expoit this as follows:
- Player A repays his loan down to £10,000.
- Player B buys 75% of player A's company, having £92,500 money and £100,000 loan.
- Player A now loans up to £150,000.
- Player B sells the shares for £112,500, now having £205,000 money and £100,000 loan. £105,000 was just created from nothing.
- Reverse the roles of player A and B. However, since B now can fluctuate his value between £105,000 and £255,000, A buys shares in B for £76,250 and sells them for £191,250 after B loans £150,000, leaving him with £115,000.
So in OpenTTD, the developers decided to 'subtract' loans from a company's value. Obviously, an empty player company still has some value, since it can loan a fixed amount of money. Thus the 6-year minimum to prevent you from obtaining a 75% share in the loan for only £3. It also prevents what's effectively unlimited lending.