While we have no real idea what the tech tree or even units availible will be later in the game, we can speculate ways to spice things up for multiplayer matches and even ai favoring a certain "doctrine".

Example: Branch off techs that lead no where else down the line were shown during the first scenario. We can use this idea to add techs such as specific development of certain units that when you invest in these techs in can lead to you being behind in other unique branches. Such as focusing on rotarery technology and unlocking different units like attack helicopters and troop transports and more advanced versions of those with different bonus'. But lagging behind in armored vehicles could be a consequence if you want to advance that specific tech.

Another example could be a branch of jet technology for supersonic and hypersonic aircraft/weapons. This wouldnt be the main aircraft tech tree but instead a tree unlocking bombers, fighters, guided missiles, and even ICBM's that go faster than their basic counterparts. Ways to balance these would to provide buffs/debuffs in comparison to regular units, such as a chance to "outrun" enemy interceptors or SAM's (during an attack with a 1/2 chance of no damage despite enemy defenses) but higher production and maintence costs and for the most part decreased range to even out their advantages over regular units. A nation sharing borders with an enemy could invest in these and find them helpful but say 2 nations at war with a decent distance might not find them useful as the distance to strike is too far.

This could be applied to a bunch of things including non military technology, and seeing how the game ends when the tech tree is fully researched it could allow a longer amount of time to be spent in certain eras. Me and a few other people I know would like ample time to experience 20th century warfare and its varietys and this could provide that for us and many others.

Please let me know what you guys think about this as I know not everyone enjoys warefare but think about what else it could be applied to.

I've discussed this before but I really hope the tech tree offers more involved choices than "when" to research a tech (in a traditional tech tree, you research everyhting eventually). I like the idea of dead end branches, and as you point out it makes a lot of sense for modern military. But it could be applied in a lot of different places. I'm curious to see what Amplitude will settle on if they do try to build a non linear research system.