Maybe try a different look at strategy, maybe high level strategy. As you said, offline time is key. I'd use this to field the best army you can, not just resources but refining (upgrading resources), unit construction, unit refining (upgrading with items and training), use of veteran units (to train new units or upgrade into command units as a teamed combat unit) and researching new tech. Like most touch screen games these choices are made during play then a time tells the player how long until these choices are available.
Online gameplay, intelligence (after fielding spies and recon units) the player uses these units to identify threats at the location their sovereign (commander, government, corporate head, etc) is requesting them to ascertain. A rough estimate (based on quality of recon units) of enemy activity indicates the position's level of risk. Battle. Split into offensive and defensive. Defensive starts with dropping start positions for combat units choosing targets to defend and patrol paths. This is passive gameplay for other players to challenge. Offensive combat has the player dropping units start positions creating a primary and secondary objectives as well as a drawn path of attack. Units automaticly follow paths to achieve objectives. During combat play the player can choose their units and activate skills (special abilities). Obviously the aim is to win combat. My addition (units that aren't killed are captured and can be converted over time) making stealth and speed the key. After combat the player fields their next army.
Combat locations are based on match making and resource requirements.