The hardest part so far has been the ship fighting mechanics.
Trying to avoid the elements of chance via dice and this has been quite difficult.
As kids we made our own paper and pencil version of space invaders / asteroids – drew a board on paper littered with obstacles – asteroids, planets, black holes etc – then a base at each side of the paper – starting at your base we then took turns to try and navigate through the asteroids by placing a pencil tip down and holding it at the top with your finger tip – pushing down made the pencil skid off and draw line – you then drew your ship where the line ended (assuming you didn’t crash into anything) . The aim was to try and get to a position where you had a line of sight to either your opponent or their base and take shots at it in the same way.
On a possibly more grown up basis though…. if you can track down a copy of Cheapass Games ‘Vegas’ it’s sort of an alternative version of Monopoly where you move through casinos rather than London streets – rather than pay rent where you land you place bets of the value of the square you land on. Each casino has a game of chance that mirrors the house advantage in a real casino so through the game each casino tends to accumalate a pot that you play for later on.
Its ages since I played it.. but those games of chance either involved dice or playing cards – something very simply like just cutting the pack and win or lose being based on the value of the suit – so you might be able to find inspiration from there for your mechanism for chance by using a deck of cards.
By the same designer/author is Kill Doctor Lucky theres the idea of luck – each player holding a finite amount of luck cards and the game play is about trying to flush out other people’s luck cards – so your element of chance might not be about the person taking the shot but the luck of the person being aimed at.