I've written the CB script (@
www.tt-forums.net/viewtopic.php?f=65&t=62868). That thing requires a nightly version currently, 1.3 might support it though.
Anywho, I've got some ideas with regards to the CB on these servers. First of all, the biggest problem is that it is too easy. What I mean is that getting optimal full-speed growth is trivial. Your company will easily grow faster in terms of cargo transported/month than your town's requirements will grow, especially in the early game, where towns take 100 days or up to plant a single house.
There are many ways to fix the issue. Here are but a few core ideas:
1: Make the optimal Rate-of-Return lower on players' assets. This can be achieved by increasing the prices of track, engines, wagons, etc. NewGRF provides support for this. A lightweight way of dealing with it involves using the BaseCosts newGRF.
2: Increase the growth speed of towns. Try very fast growth speed. Towns can't physically grow faster than one house every 2-3 days though.
3: Increase cargo requirements.
4: Instead of having the challenge be 'build speed' (which is pointless since it's trivial to max your town's growth speed), have the challenge be 'network capacity'. By greatly increasing the goal value, the cargo requirements will put a strain on networks that aren't well-designed. The game's length will be drastically increased though.
Beyond the main issue, there's some smaller things that are weird.
1: Disabling of control-click building is annoying. For example, if you want to transport stuff literally one tile, building a road-vehicle 'switch' is about ten times as much work. A road vehicle switch is a row of two alternating RV stations with unidirectional roads pointed towards them. RV's are trapped within that switch. They stop at each of the two stations every tile they travel and can then dropoff ~150 cargo per RV per month.
Not to mention that there's many legitimate configurations of stations and waypoints that cannot be built.
(1a: Although, you could try it with docks since ships can quantum-stockpile...)
1b: If you do enable control-click building, issues with station spread may become apparent. However, station spread is limited by max. station size setting. You can't really do evil game-breaking things as long as you load under the station sign.
2: Default RV prices are too expensive compared to trains. A two-tile train has equal capacity to 4 road vehicles, more speed, and less cost (with the right loco). Plus rails are cheaper than roads. RVs are dreadfully slow. I suggest EGRVTS or Basecost modding RV prices by 1/2 via NewGRF.
3: Default Lumber Mill cuts trees. This means manually planting trees. This is a chore, not gameplay. How about using either LL's lumber mill GRF (which disables cutting trees and increases cost by 20%), or using OpenGFX+ Industries GRF?
OpenGFX+ Industries allows you to choose the type of industries for each industry chain. You can e.g. have coal in desert. Or have
forests of tropical trees instead of lumber mills. This fixes it nicely.
4: The game has no money sink. That is: there's no way to spend your money apart from building trains/tracks. This means if the goal is raised or the game's effective skill cap is raised, building fast is the main thing. This can be good or bad, depending. For now, I don't think this is a serious problem at all, it could be just what makes this unique.
5: Cities grow by transporting passengers to them. Depending on future development, making the game harder in some way, this may create a "Tragedy of the Commons" (see wiki article:
en.wikipedia.org/wiki/Tragedy_of_the_commons
A company that uses a city's passengers for its own town gains more than one which grows a city. In fact, the latter can aid the former to its own detriment. As there is currently plenty of city on the map (and players are stupid and don't unload and leave empty in their own towns), there is no huge cause for concern. Later on though, you might want to change the growth req to transporting passengers
from cities instead.
6: Very small towns may be ungrowable. They may not accept mail or passengers. There does not seem to be a clause for this.