As far as battles go, I think the thing I would like to see is enemies that are more intelligent and able to prioritize targets, use cover, work as a unit and be aware of their health (like the elites in halo would hide to regen their sheilds). Now that the queens are dead and primarchs are the order of the day, squads with a command heirarchy should work well. The primarch or commander should be a more cautious and powerful member of the squad, but other squad members should not (edited) be fodder. In this way you can have epic tense fights with fewer enemies. We got something like this in R2, but enemies were either nothing more than fodder, or they would just rush you.
I like the idea of arena type areas where you and your team have to manage your areas of control, where a sense of scale can easily be accomplished but the player can still feel claustrophobic, and where enemies can come from any and every direction without it feeling like waves of mindless meat to mow down. I want to feel like I am playing a game of cat and mouse, where one moment I can feel super powerful and then immediately feel like the roles have reversed. This is what attracts me to games like Halo and the online of Bad Company 2, but the diversity of enemy types in the Resistance universe, if presented right, could be a whole new level.
With that said, I thought I was really burnt out on the franchise after R2, yet here I am excited for every detail I can get my hands on. Looks great JS, thanks for keeping us informed.