Make sure you have all the usual safety gear: life vests, throwable, fire extinguisher. A small first aid kit is a really good idea. I can't count how many times people have cut themselves on various items and needed some wound cleaning.
I can't emphasize KEEP A KNIFE ONBOARD enough. If you ever suck up a rope, you will need it to get mobile again. Besides that it comes in handy. Be very careful if you do tow sports to keep the rope away from the back and underside of the boat. The rope can get sucked in faster than you can blink and if anyone is caught between it and the hull they will be in a world of hurt. Make sure you have somebody in charge of rope management if you are doing tow sports, but don't trust them. I use a little foldable utility knife from Home Depot. It has served me well.
Almost as important as a knife is a bottle opener. As far as the center for a cooler goes, I did think about that once and posted a thread on it. I think the consensus was that you would need a boat load (yes, pun intended) of ice, and it is not insulated so the ice would not last very long. The nice part would be that if you leave the plug open it would just drain into the bilge and you could pump it out with the bilge pump. I have found the center storage the best place to stow coolers though. I used to put them under the seats but I hated having to move seated people constantly in a small(ish) boat.
I use these coolers from Bass Pro Shop. They fit the width of the center storage perfectly and have held up with a lot of use now for 2 years. I use two. $16.99 each:
http://www.basspro.com/shop/en/bass-pro-shops-soft-side-cooler
One other mod that sounds dumb, but it is probably the easiest and my favorite is the storage compartment garbage can:
https://jetboaters.net/threads/here-is-a-great-trash-can-idea-for-the-storage-compartment.14318/
Performance wise, the only thing I can think of is if you are heavily loaded in the stern with nobody in the bow, you might need to move one person up there to get her up on plane. If this is your first time with a jet drive, it takes time to get the hang of things, but don't get discouraged. Once you figure her out, you can far out maneuver any sterndrive. You'll learn to anticipate the wandering and figure out how to preemptively correct for it. When docking use very slow speed and small pulses of the throttle in and out.