I think Warwell brought up a great point about using relatively simple rules, as rules with enough complexity for two players can quickly overwhelm a solo player. I say can, of course some solo gamers are in love with the process and so they enjoy the added complexity, but I’m definitely in the ‘keep is simple’ crowd.
And Shaun’s absolutely right, you don’t necessarily need a campaign with characters, you just need an impetus beyond wanting to be a wargamer, something specific to drive you. I find (in my rare face-to face games) that just wanting to play a game is enough, because you’ve got the social interaction, but my solo gaming is more goal-oriented, I.e., I want to see this unit through this operation, and the next, and the next…
“And you do have gaming friends Jack, they just live thousands of miles away from you. No idea why”
Just wait until I pick up and move to Brisbane!