The Kowal oversized actuator for the JLF fits the Hayabusa perfectly. As far as springs, I like the stock spring myself, but order several and swap them out to see what you like best. A lot of people prefer stiffer springs, but Old Man Arthur surely does not.
My Hrap 4 Kai has an octo gate, oversized actuator, bat top, and that's it. It's near perfect as a general purpose stick in my opinion. I don't care about octo gates for shooters though, that's more of a fighter thing.
I do have an old Xbox 360 stick with a Seimitsu LS32, and I've rebuilt some Neo sticks recently using LS56 parts. Specifically for shooters I may like them better, but the Hayabusa is a great stick on its own and you can put it in the same class for about $10 in parts. If I had an empty case and my choice of any stick to use I'd go with Pretty Amy's suggestion.