This is a suggestion I really had to make. I don't know if an addon in this regard exists for pak128, but personally I think it would be a wonderful thing to have by default.
In Simutrans / pak128, the player can start from as early as year 1900. They can let the world evolve until it reaches our day, all the while unlocking buildings and vehicles and roads at different years. This accurately represents history and how certain products and technologies were researched and became available; The items you have in the 30's look like what existed in the 30's (eg: coal trains, cars with spoke wheels), the products available in the 60's resemble our world in the 60's (eg: jet planes, modern looking cars, commercial glass buildings), the 90's look and feel like the 90's (eg: early electric trains), and so on until we reach our time period.
Unfortunately once we play past roughly the year 2020, there is no new content to unlock. This makes sense as we're currently in year 2017, thus we don't know what's going to exist years from now. Yet why not use what we can estimate to build up to a more distant point in history, perhaps even a century from now? After all we do know how technology in the future should be like, based on scientific news articles and even existing prototypes that were built and tested! It feels really off and demotivating to continue a game down into year 2100, only to keep seeing the same houses and cars that we have today... it makes no sense, we know it's not gonna look like that then! For this reason I'd like to suggest considering buildings and vehicles covering the future time period, and letting them be unlocked when reaching year >= 2030 / 2060 / 2090.
Some examples: Hover cars were already tested, and we know a few models of floating car are likely to be commonplace a few decades from now. Likewise we're likely to see towers with grass / farms / trees planted on top of them, not to mention dome buildings. There will also be hologram advertisements on buildings.
I know an argument against this will likely be "the default pak64 / pak128 is meant to be historically accurate, we can't add something we don't for sure will exist as that would count as scifi". In my opinion though, this only makes it less historically accurate, since we know the world won't look like in 2010 once we'll be into 2050! It seems fair to use all knowledge we have of upcoming buildings and cars to estimate what will become available over the next century... then as time goes by (in real life), assuming Simutrans will still be in development decades from now, we can correct graphics and specifications based on what we were wrong about. Besides... if anyone wants maximum historical accuracy, there would be an option to cap the timeline year to our real life year using the system clock

What are your thoughts on this?