I would reconsider your pack choices, 9.6v1600mAh sounds like a Radioshack AA flatpack and those aren't great, IR is pretty bad, they are not much good at high current. For blades, they will not get you what you want, I know someone who used one and had an unsatisfying windup (trustfirish) out of blades on a stryfe. You don't need much more than 8.4/9.6V to get max velocity out of blades - I would do it with 7.4 personally but I can see going higher for a little boost.
So, I would recommend a sub-C or good quality 2/3A 7.2-10.8V nimh pack or a 2s/3s lipo.
Wouldn't use that 19.2V, that could have complications, and if you mean to avoid trustfire type solutions, it's the wrong approach. You don't need half that voltage when the battery has guts.
PWM wise, there are current limiting drives and non-limiting (like an RC ESC) drives, and if you overload one of the latter, magic smoke may occur.
IIRC the stall current of 2 Blade stock 180s is around 45A on 2s, 60A on 3s. Check the specs on the PWM controllers for burst current handling. You may be able to get away with less but I know from experience that mosfets and overloads result in inopportune emission of magic smoke.
I hate to say it but I am of the opinion that flywheel motor PWM as a standalone addition to a gun is not that practical. I like to keep this high current electrical stuff as clean and simple as possible.