On paper, this is a great idea... small primaries, coupled with large secondaries up stream. Keep in mind the costs and complexity go up significantly... double the injectors, double the fuel rails, double the mounts/bosses, potential accessibility issues with the secondry set, blah, blah, blah.
Actually, what you're referring to is 'staged' injection. Sequential refers to the injectors being timed with the valves, opening once every other revolution. As opposed to batch-fired, opening every revolution with disregard of valve timing.