In Wôbanakik (Dawnland, Abenaki land) there is a similar system called the “seven sisters”. This includes the three sisters, but also sunflower, sunchokes, ground cherries, and tobacco.
https://vtgardens.org/the-seven-sisters-of-abenaki-indigenous-agriculture/
In the South, native people would plant mulberries and other fruiting plants amongst the garden plants, and when they moved on from cultivating that spot, it would still provide fruit.
I think you can add as many plants as you want and it will still come out lovely!