I do think space invaders combined with either pong or snake or breakout could work well. It would be cool to discover what game you get by mixing different classic games together and see how hard they would be to play. I have come across a game, not on this jam, but which was like snake and pacman, and it was a really good puzzler, you collect the dots and get longer as expected in a maze and then have to plan which way to go so you don't crash into yourself, I don't think I will find it again as I've forgotten what it was called. But you can definitely make some nice combinations suitable for any skill level