Research improving player control options, more than a +1

It’s a bit of a vague title, then again it’s a bit of a vague concept I’m opening up here. In Aoe2 there was the Ballistics technology that made ranged units lead their shots when firing at moving targets. Having the upgrade makes a huge difference in playstyle, yet it’s not disruptive enough that any gameplay before the upgrade feels like playing an incomplete or unpatched game. I guess the farm-queue is sort of similar to that too, you can only make a queue when you have a mill, you need to manually refresh your farms until you have one. (It’s not a great example though, it barely ever comes into play that way at all.) And there was of course already the anti-miss Thumb Ring technology. These techs separate themselves from the masses by not just giving a + to some number (build speed, carry limit, attack speed, attack, defense etc). Instead they have a very dynamic effect on the game. Something that makes a difference you can observe directly rather than just through its effect (enemies fall dead faster etc, also movement speed is a bit of an edge case as described here, but it’s common enough that it doesn’t really need to be discussed). (Technologies or buildings that unlock units, buildings or other techs such as the barracks, chemistry or the age-ups don’t really count either, they’re pretty much a category of their own. So a tech that let’s you make flying units wouldn’t count, a tech that let’s certain existing units fly would.) That made me think: what other quality of life improvements could take an ingame spot in a new title? And should they?

One thing I could see happening is formations. Military drills are not something that has always existed after all, and tactics and troop training tend to get more complex in times when lots of time gets invested in being better at war. So there could be a technology that either unlocks proper formations or just some advanced formations (box, flank, ranged behind melee?) somewhere during the game. I don’t think attack-move should be an unlockable, but if attack-move is in the game possibly patrol could be (part of) a technology, improving your vision of your territory and arming your troops against surprise attacks.

Now, I’m not that up to date on more modern RTS games, so I suppose many of you can teach me a thing on two on this topic. Therefor I’d like your opinion: what kind of options would you like to see in Aoe4 that are not so essential you need them during all ages, and might in fact be most fun as an ingame advancement, providing you with the right type of quality of life improvement at the right time?

Because we don’t know when or where Aoe4 plays out, suggestions that would only work in certain time periods (or even ones that require a mythological component, if you can think of any) are all welcome. I’m hoping to see some interesting options, because this feels like something that can be milked to a greater effect than I have personally seen done yet.