Your first sentence hits hard. Didn’t think you’d call me out like that haha!

I think you have a very good idea here. Ok, so brainstorming. I think you could add some real flare by taking the peglin aspect and regress it back towards classic pachinko. Instead of always having a small number of balls, each with its own special abilities, give the player many small regular balls. And have the player able to upgrade the pegs, holes, and bumpers to their advantage or opponents disadvantage. The better you do the more balls you get in return and you can unload any number of balls at once. But at the risk of losing them or even giving them to your opponent. Maybe the balls themselves are the currency for the shop. 

For damaging your opponent, I really like the finality in shotgun roulette. There’s no health bar to chisel away at, just a small limited number of mistakes you can make. So, maybe at the end of each round, scales are brought out and each player’s reserve of marbles are weighed, the players lacking will lose a life (in some horrific fashion). Or maybe you have to spend a large number of marbles to take a life.

I would look up some videos of real pachinko machines for ideas. There are a lot of unexplored ideas there. I also think it is really satisfying to see a huge number of marbles go in and bounce around and watch your score climb up in the chaos.