No pak set I have seen contains two buildings which differ only by the addition of a few extra rooms. Simutrans would not see the connection, and know to replace one with the other. In addition, buildings in Simutrans supposedly represent whole city blocks.
So you are willing to suspend your disbelief for one building to represent a block of building, but not for one building to represent an extended version of something represented by a different building before. oô
Once an area reaches too high a level, it becomes to expensive for industry to stay.
I was under the impression that industries own their facilities. They don't rent them, so changes in land value only make them richer in the books. It's not too expensive for industry to stay, if anything, it's too expensive for industry to come after another industry went away for different reasons.
Furthermore, the level only indicates the buildings expansion. If it was land value, it would need to be stored in the ground tile, or new buildings would need to start at a higher level based on their surroundings, because they would be in a high-value-area.
In post-industrial Europe, cities are becoming commercial and residential only. What little industry remains are big complexes, typically out in the country side, which are represented in Simutrans by factories. Although even they are dying out in real life.
We shouldn't mix up factories with industry, that's a whole new bag of worms to open. You need the industrial buildings to represent smaller industries which live in the shadow of bigger ones. Otherwise, you'd need to get rid of commercial districts in favour of end-consumer-shopping-malls as well. (Pretty sure Strømmen Storsenter would be one of those, rather than generic commercial buildings).
But yes: Large industrial districts do tend to form outside or at the edge of cities. And it would make sense if an inner-city industrial district was moved to the outskirts. Either by building a new industrial building outside once the inside building was replaced, as you suggested, or by designating a larger industrial zone and planting higher-level buildings there, while those in the city are abandoned.
Because those new, outside industrial districts are not low-level, they pretty much start out high-level as a grand project, rather than natural growth; or because one large industry is placed there (a factory in the game) and other industry follows. Same is true for commercial centers, a large store is often buildt on the outskirts and other, smaller stores build nearby, creating a commercial district.
The problem here is that there is no representation of that in Simutrans, at all. IF the industries can't pay bills in the city anymore and move somewhere in the countryside, as you claim, then
A) countryside industrial districts should start with higher levels, especially when city-districts get invaded.
B) countryside industrial districts should grow faster than city districts, as they are cheaper (why would there be a switch at a specific level?)
The city I currently live in was founded on industry, focused on the river, in particular the waterfall. The early industries near the waterfall have now been replaced by shops and apartment buildings. Even the hydroelectric power plant itself was turned into a television studio. (The waterfall still generates electricity, but in another, newer and much smaller building, which likely has a lower passenger level.) The last major industry within what one could call the city (Norwegian cities don't have formal borders, except Oslo), closed a few years ago. It hasn't been replaced by commercial activity, but by a railroad timber terminal and some smaller industries. A bit interesting, since railroad terminals and sidings elsewhere are being replaced by commercial and residential buildings. The city has now reached a higher level of development where it no longer depends on industry, but commerce (and government agencies) to employ its citizens and generate taxes. Maybe capping industrial levels below commercial levels in Simutrans is meant to reflect exactly this.
I don't think so. Industrial levels are not exactly capped by the game after all, they could be just as high as commercial or residential buildings. It's just that there are not too many industrial skyscrapers in reality, it's more of an accidential interaction rather than an intended solution to anything. Pretty sure Prissi mentioned at some point that it works if it's done as intended, and showed a screenshot with pak.japan and industrial highrises. So the Intention is to have all types of buildings at all levels. If you go back to the start of the thread, that's what I want to do - just with less pax and post for those high-level industries.
The only thing missing is that the same thing does not affect factories, although that should also involve factories being upgraded, probably to new versions with greater production, but less passengers and mail. A few industries do remain in the region around the city I live in, but quite some distance from the city, and they are doing modern high-tech stuff with fewer workers, so they likely have lower levels than the industrial buildings of old as Simutrans would see it.
That's the situation in Norway. Meanwhile, my closest large city (Linz, the Steel City) has traffic troubles due to all the workers coming in each day, as about a third of the city is industry, most importantly the Steel factory VOEST. The actual core, around the townhall - what would rise highest in Simutrans - is still old buildings. There is practically a ban on any development there, so it's commercials on the main street and otherwise residential, mostly low levels. The highest commercial levels are probably the office towers at the railway station, otherwise, it would be malls like PlusCity - far outside the center.
Perhaps in 50 years, the city won't be industrial anymore, but changed to third and fourth sector as well, while steel is produced somewhere in africa or asia. But until now, it did not.
Once more: The current mechanic is no good. It does not do a good job at representing what you see in it. What you want to be represented could be represented, but the accident that currently exists is not the way to go. And I don't even want to change it per se - all I want is two silly parameters that don't even need to have anything to do with this. There must be some place in the code that says "Set the pax of this building to level*bits_per_month" that I want to be changed to "If pax_level is Null[Set the pax of this building to level*bits_per_month]else[Set the pax of this building to pax_level*bits_per_month]". Why do we need to have a discussion about how industries in reality grow and get replaced just for something as simple as that?