With this optional rule, every frame has their own initiative. If a frame has less than four systems, roll 2d20. If it has four systems, roll 1d20. Leave the dice as markers next to the frames.
When a round starts, tactical order starts with the frame that has the lowest number, and goes through the sequence, up to 20. If a frame has 2d20, you can pick which one to use as soon as your lower number comes up. Once chosen, the initiative remains for the duration of the game. Alternatively, roll again for every new round for even more chaos and unpredictable outcomes.
While this adds considerable amount of time to a round, it opens up for a more varied playing field and tactical options. Keep in mind, though, this favors attackers, that normally have the lowest initiatives.