Theoretically, an inline needle valve would work. In practice, the majority of people that uses regulators that aren't tried and proven have some issues with bubble rate control. As it is even with the deluxe m3 system we carry, which is probably the best unit available/possible, bubble rate control does require patience.
It boils down to use. If it is for a freshwater planted tank, it'll probably be fine. For a calcium reactor, I doubt it will give you the kind of control you would like.
You can always give it a try first. If the regulator doesn't bring the pressure down enough, then you can pick up an econo regulator from us without the needle valve.