I mean the technology isn't lost. Some people have argued that being forced to build the 'currently' unlocked unit is game breaking because production was flattened with the launch of Fabius.

We are not going to produce archers in the industrial era. 1 because no civilization would do it in the time of guns and 2 because yes, we have some of the know-how about the bow and the tactical use of archers in armies.

And above all, it's just a feat. Guys put archers in their bar to either use them, because obsolete units can do too much damage against modern units, or more likely to upgrade them with a nice gold bank.

The best thing would be simply that any unit that is two eras behind if the technology is mastered, is automatically transformed in the production bar, into the modern unit.

So if you have archers in your bar and you can make crosbows, they stay archers. But if you can make harquebusiers, your archers are automatically transformed into arquebusies.

One could argue that giving out modern rifles to a unit will have the same cost whether they'll be giving up their muskets or bows, but being able to skip pop cost that way is a bit gamy. Maybe the additional pop required could be calculated into the upgrade cost, i.e. if original unit costed 1 pop and upgraded costs 4, then gold cost of healing unit from 25% health (1 pop vs. 4 pop) would be added to the upgrade cost?

That and maybe tweaking upkeep to be (more) dependent on current era, rather than the units themselves, to discourage purposefully keeping the outdated armies around.

I always hated how some 4x games make you delay progress to train soon to be obsolete units.

And my most annoying scenario, building the unit to 90% only for it to be changed to the next era variant costing 4x the production.

So, I like how Humankind handles it, but some limitations are needed.

- like clearing queued units that are twice obsolete

- removing units from the queue after x turns

- or even freezing the queue when it contains obsolete units (you either allow the queue to complete, or you have to remove the obsolete units if you want to change the queue)