Wow, the idea is really not bad at all. But it takes a lot of work to make it happen.
Not necessarily! I made a solo game up for playing on a pool table:
Rack up the balls normally. You can hit in any ball at any time. However, if the cue ball goes into a pocket, you have to put balls back on the table, as close as you can to the place you normally rack up the balls to start. The number of balls you need to remove is the number of balls still on the table. (So, if you are down to 3 balls still on the table and knock the cue ball into a pocket, you have to pull 3 balls out and now have 6 remaining.) If over half the balls are on the table, you won't have enough to put back on the table, resulting in a loss. If you can clear all the balls from the table, you win.
You can make the game harder by requiring each shot to be called.
There you go: simple rules, fun game, teaches you to think about where the cue ball is going to go after the initial collision.