First off, per old tradition:
well done borg this is amazing holy crap
Second, my actual feedback, if you care for it:
Been having an absolute blast with this like I haven't with the game in a long time, always cool to see the occasional spicy grf to go with all the gravy grfs. Really liking the curveballs you're throwing. There's only a couple of things I'm a little iffy on.
First and foremost, the primary industry reserves - I'm not sure I'm playing around these correctly. On my first attempt, I managed to get my coal mines to produce 2K/month and they all shut down super quickly. You're saying they're gonna last 50 years on 300/month, but AFAIK the only way to keep production that low is to provide a crappy service? However, that way you're not gonna be able to give the power plants the fuel they crave, and the secondary industries the power they need to chomp through what you're feeding them. Maybe feeding a power plant from multiple mines kinda crappily is the answer? Even if that's the case, in the end, they just close down anyways, so maybe don't bother laying down actual infrastructure?
So anyways, here's the ultimate solution I came up with: a giant fleet of coal zeppelins all bound for the singular holy power plant. A service just crappy enough to keep the mines going for a long while, yet when they do close down all you gotta do is remove the heliport and build it elsewhere. I don't know if that's the intended solution, but it's what I arrived at. Maybe I'm just stupid. Maybe I just really like the sound of a giant fleet of coal zeppelins. I am definitely stupid.
Then the second thing, which I'm significantly less iffy on, but still kinda - the valuables. In the vanilla game, banks never produce them in great amounts, so you really just want to stick to the occasional armored car making the rounds now and then, in that nice and believable kinda way. Now with this GRF, you're saying at 10K city pop the bank production maxes out, which I'm seeing at like 600-something/month. I'm iffy on both of those numbers, but I guess they might make sense behind the scenes, to keep the primary industries properly fueled and whatnot. Whatever the case, what I ended up doing is I have a bunch of big old superfreighters full of gold bars to ferry the valuables between the cities. Don't tell the Somalians. As it also happens, most of my cities are well over 10K pop (with my settings, 10K is really the starting size), so my map is more like a weird alternate reality where the holy crusades never stopped and we're paving the streets and the countryside in gold, spreading it on bread and bagels too because why not.
It just seems weird to me that valuables is what you want to transport in large quantities to keep the city's stocks full, it seems more like it'd be a once-per-month resource. You know, like what goods is currently. Come to think of it, wouldn't it kinda make sense for goods to be the large volume resource for towns to stockpile, hmm? Maybe valuables could provide a simple binary boost to the primary industries, and the volume of goods delivered would be the limiting factor to town growth - if that's possible? If it is, it could give the player a way to precisely regulate the rate of town growth through gameplay. If not - well, bummer.
Oh yeah, and another thing about the boost from valuables - I'm pretty sure it was a contributing factor to my mines mining out super fast, these two mechanics don't seem to love each other too much - unless I'm remembering wrong and mine production isn't affected?
Last but not actually least - temperate is a great climate. It's fantastic, really, and I'm glad you're enjoying it to the point that you were inspired to craft this little gem for it and it only. I lied though. I hate temperate because it smells like old socks. I'm still glad you crafted this GRF though, that part is 100% true. And I totally get that you can't simply take the temperate template and paste it over the other three. And I know that the best course of action after writing this all down would be to grab the source you provided and stumble around trying to learn NFO from scratch and use it as helpful guideline towards creating my ultimate blissful experience that I would then share for everyone else to enjoy and moan about in much the same manner I've been thus far, but uhh... I don't know if that's gonna happen. I know I got no excuses in the quarantine but let's just say if somebody else nodded to any of the nonsense that I just said and is more bored and motivated than I am to gracefully go ahead instead? I don't know where this is going. I'm done typing now.