It would be interesting if the developers decided to make an annihilation, non-power-core mode with different, more lore-oriented stats and mechanics for this game, as well as less animations and more background oriented focus.
(No need for this to be extensively oriented, as I believe power-core was the mode which focused in competitive gameplay).
For example, tactical marine squads may cost more and have fewer members but deal and sustain far more damage, orks may be cheaper and more abundant but far more vulnerable at range assault, say a squad of 10 orks may be cheaper than one of 4 marines and get wiped out when in ranged combat but if they manage to get in close combat they may have a fair chance to kill the marines.
Building mechanics could be similar to DoW1 while still retaining the hero units DoW2 styled powers, and elite units may be unlocked by the tech tree but have a numeric limitation (for eldar too, no 3 squads of Warp Spiders this time) so basic units may still be useful, as for the cover, since it's not implemented there could be a new skill named "go to ground" which gives armour bonus at the cost of speed movement, hence avoiding the need to reprogram most of the scenarios, another possibility is to have transports have a "cover" aura which increase the damage they receive by certain percentage but give bonus armor to close troops.
Finally, it would be great if these races had access to some sort of nukes C&C style, they may need a considerable amount of investment but may deal a lot of damage.