I didn't know what to call it, but "warzone 2100" has the tech tree which you have to fund to research, before making your own custom units. Now what I'd like to see with OpenTTD, is a similar version to this, albeit not with the intentions of annihilation or war, but research to make newer vehicles available. Obviously all aspects could be "researched" by the player using the existing framework/new grf's or new concepts yet to be thought of or made.
Therefore in a new game, everyone starts off with the slowest vehicle of each type, one train type, one truck/bus, one boat and one aircraft (aircraft subject to change), there are no advances by default, so when a new train would normally come in, in this version it doesn't. The only way to get to use a newer/faster train is to research it, but unlike warzone, when research has been completed, it becomes available to all, not after a delay for others, however the original researcher (the first to research a particular vehicle), gets a commission every time another player purchases that type. The only way a player can avoid paying this commission is to research that train themselves, which is turn would be added to their own completed research table.
This whilst not directly linked to CB, could also be used in-conjunction with CB games, so that higher populated cities can increase their research percentage, which in turn for both non CB and CB games would be a percentage agreed by the BTpro community, say 8%, which is not to say a company worth 1 million can pay 8% to get their new vehicle at the same rate of a company worth 10 million contributing 8%. The percentage is what can be changed by the player as and when they have the cash to invest, however the maximum should be something like the 8%, and only increments below this can be changed by the player, so like 0.1% on a sliding bar up-to the max of 8%, when the research reaches a certain value (for example £500k for 2nd train) the research is completed and shared to all exiting players, with the commission aspect detailed above.
Of course a new research building sprite will have to be made, and probably a new button to be added for the sliding bar of research, both of which are beyond my capability. I'm in my opinion am just an idea's man.
This idea will as a result if implemented make for a more interesting dynamic to the game, as well as helping more companies go bankrupt due to reckless researching.
Of course the aspect of Warzone 2100 to make custom vehicles using their constituent parts could also become a reality, but for now, i'm just explaining the idea of a research option.