Small update (Apologies).
As I've been trying to build skills to motivate myself and to keep to the choice of motivation in all times I make said choice, I'm finding that making The Fallen Ages between September and December in any capacity isn't realistic. This isn't so much a delay, but informing everyone interested in this project that work will start in September, but it's not going to be at a rapid pace, I'm not yet capable of it as I lack the skills necessary to work that much (and am trying to unlearn my hate of working). I've decided that I will be treating this like the Early-Access version of a kickstarter, just with no money involved of course. I'll upload concept art I end up making for the project when I can and try to be more involved with sharing progress, it's just probably going to take a full year for a playable build to happen as I also work through just... sooooo many projects. Might be spreading myself thin, but I'm enjoying it a lot so far.

Yeah I plan to eventually resume work on this, since the idea is to effectively create something different, it means I can create a game I can enjoy much more. For now my plans are to work on a Factorio TC mod to do something similar as well as start a couple of things and try making something for PirateSoftware's 15th game jam.
I expect to be done all those things by the end of August, so I'll put this on my list for September and onwards

I like your ideas for sure, they're getting me thinking, and thank you for sharing them, you also reminded me that I ever started this project at all, to be blunt, my then-unmedicated ADHD started this project, and promptly forgot it even existed.

Thanks for the reminder, I've started to think more on this and have even more ideas I may put above, like possibly replacing Gold with Iron. I think I will make a forum post with said ideas, or not, I'm unsure.

hoping you come back one day:

what could also be interesting, is making ageing-up and building castles (and stone walls) take much longer and cost wayyyy more.

but also making castles and stone walls much, mush stronger.
(love the idea of castles needing garrison to fire like tc)

so the end result is that everything in your base is cheap, weak and fast to replace. but going up to a new age requires not spamming units, saving till you can and even once you manage to hit that button, it will still take so long to actually get the benefit of the sacrifice that the wait might kill you.
which seems like how it actually works in history, the less advanced the age, the longer it takes to escape that age.

simply, investment in the cumulative advantage of tech if often outweighed by the imitate advantage of investment in scale.
aka
one day you will have 1 tank 5 times better than the 5 tanks i have now, but i have 5 tanks now.

awesome idea. I really like the direction your thinking in!