Re. multi-player electro-mechanical games, the additional complexity in the machinery is usually cancelled out by the lack of same in the game rules, since there's no 'memory' of an individual players' achievements ball-to-ball. Even when playing a multi-player game in a single player situation, the objectives tend to reset between each ball, rather than holding over for the duration of the game. A famous 70's Gottlieb game, El Dorado, appeared in single, two, four player and export guises (and even an 80's solid-state remake), but was probably best as the single player original