OK-
-Easy and cheap would be to add a dry 50 shot. Pretty easy to tune and setup but limited on use and practicality.
-If your looking for tuning what you already have you'll need to find someone who can work with the Seimens ECU. Look at the performance Seadoo forums and hope for someone to play nice. Right now there are only 1-2 guys who can do it but they will not likely know what parameters you want changed. Also, most of those guys aren't into sharing unless you know someone. Maybe AF1 can help with that end. Worth a call.
-Stand alone Motec. A kit doesn't exist that I'm aware of but probably the best Motec tuner in the world happens to own a spyder (is on here time to time) and could chime in if it's possible. I'll let him decide if he wants to share....
-1050 Aprilia kit. Full Aprilia electronics. Maybe add a bigger wet shot on top of that?? Easy 200+hp.
You really need to decide what your looking to do and what you want to put into it. Your not going to find the info you are looking for on here. This just isn't a real performance oriented crowd. AF1 is probably the place to be to read up on these motors and tweaking.
If you do dig into it, post a build thread. I'd for sure be interested in reading it! Good Luck!