Modularity would be great too. Standardized connectors and outer dimensions for engines even between brands. Medium, large, small. You don't need 100 different types. Meanwhile, all this has been overtaken by the need to get away from fossil fuels as soon as we practically can. Oil should not be valued based on the cost of pumping it out of the ground but based on the cost of creating a liter of it from raw materials (CO2, lots of energy).