I don't know if this is still open to suggestions, and as I haven't read much other than the initial post, I apologise if this has already been suggested.
My idea is to get a few units and some funds and a hack report of a "target" you need to beat. Should you win, you continue to the next level, in which the target is a little bit more difficult. Over time the opponents get stronger and stronger, and as you progress you can "unlock" new techs and units, and your funds can increase. And you can save unused funds from previous levels and use them later on.
Perhaps have different tasks as well. Here's a hack report of someone, here's the money and units available to you, your goal is to land on him, kill his hamster, profit from the attack, defend successfully, and so on.