"Units should be able to gain ranks"
this is good because its promote preservation of units.
could be bad if experienced vastly overwhelm greenhorn units (any MMO rpg allow you to taste this in pvp). Also in Tzar it leads to cheese stuff like training on dummies to have powerful army, instead gaining xp from combat.
"Neutral units"
Neutrals are great map decorations. Would be neat to be able to gain their favour, intead only being seen as enemies.
"Cover"
Cover could also hide your units. Grant them invisibility (till they not attack).
"Attack types"
and armour/size types. This would have to fit the game. F.ex. in space RTS there could be bio, mech, energy... hard/fragile (aircraft)... small / big.
While in medieval setting: heavy armoured or not (different weapons - mace is generally worse, but do well vs armored knights compare to sword that is useless), mounted, on foot, flying + obvious magic/fire/elemental etc
"Units should be readable on the battlefield"
limit zoom out. or fixed camera.
"No hero units or RPG elements"
Hero units in Warwind (this game is trash, but have some clever ideas) were obtained when player was losing. Neat rubber band mechanic, as difference in player skills tend to end games prematurely.
"just get gut noob"
Not sure if you realize, but towers (defensive structures) are rubber band mechanic too. That force the rushing player to tech up to siege equipment. Otherwise, RTS games will end in minutes.
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"Total Annihilation / Supreme Commander RTS lineage"
Loathe conga lines gameplay with almost no-micro (and i generally dont like micro, APM etc).
but this games have such a lovely scope - water, submarine, land, crawling over mountains etc. compare to limited games like Godsworn.
Also BAR UI is a masterpiece. Learning new ways to control your units there is an absolutely brilliant experience.
Recycling (resurrecting) corpses. Shooting resources (plasma guns, D-gun use your energy as ammo).
Water gameplay. Nukes gameplay (counter nukes).
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"Myth and Myth 2: Soulblighter RTS lineage (I remember they had some cool features)"
Gore.
Competent melee units.
Physics of grenades.
Legendary ambient, narrator voice, and mission fluffs. It is gamified black company (glen cook).