another (for combat) would be making units much faster and projectiles slow and very very prone to miss without target-leading and have all the units have their own target leading.
This was the case in Supcom. it's very clever because you can of course micro units to hit a specific point but your own unit's AI was already doing something infinitely better than what even the topmost starcraft II player could ever manage in terms of micro.
This is perhaps not the best thread for this, but this is a very important point regarding micro.
The best way to do this type of large-scale warfare is not to build units that are inherently un-microable (e.g. perfect aim, unresponsive movement, etc.) but instead to give them AI that is better at micro than you are. And simultaneously to give the player so many units that micro is just not feasible.
It is still very important to have tactically interesting combat, even if the player is not going to manually manage the tactics of every engagement, both because the AI is dependable and because it is mechanically infeasible. Strategic decisions should take notice and take advantage of tactical features on the small scale. Like making the observation that arrows don't fly well when it's raining prompts a savvy commander to choose to attack into enemy archers in bad weather conditions. Interesting oddities of tactical combat can be writ large over an entire army, and actually have a significant impact on strategic decisions.
There are lots of ways to have tactically interesting combat that theoretically the player could micro. Maybe a unit fires a linear projectile in a straight line, which would make it scale weirdly against small numbers of fast units juking left to right, but pretty dependable against tightly packed groups of the same type of unit. Weapons with dispersion patterns, deliberately inaccurate weapons, splash damage, dodgy guidance, and other features can have a big impact on the strategic aspect of the game.
The philosophical difference is that if you have 10,000 units it is patently obvious that Starcraft style micromanagement is likely not going to mean much in the grand scheme, and that's even assuming you can outperform their AI. Which is doubtful, since AI is potentially VERY good at mechanical tasks, like shot dodging, aiming, or target firing. I want to see lots of inaccurate weapons, lots of missed shots, patterned attacks, with units in pitched battle moving around actively engaging the enemy, both trying to deal damage and avoid taking damage. Every projectile is simulated- you're already paying the price necessary to implement this kind of combat, why not actually do it, rather than infrequent firing of highly accurate, normal, boring weapons?
This has the side benefit of making the actual unit fights interesting to watch because the outcome, although relatively deterministic, is actually more difficult to predict than a direct comparison of force size. Clever stratagems and tricky plays can let you win battles despite being outnumbered or outgunned.
The converse of this is that if you make a completely bland blob where units deal consistent DPS perfectly with no special behaviors or properties, then you know exactly what is going to happen strictly based on force size.
The opportunity to outmaneuver the opponent by fighting a tactically superior, highly efficient battle is greatly reduced, because the way you "win" a battle is by deploying more units to fight it. And the only way to gain a real edge is by destroying soft targets for free. In a normal game you won't typically get far ahead just by repeatedly colliding armies, at least until you outproduce your way into an army advantage and start winning each successive battle more decisively than the last.