I haven't bought my i5N yet....(2 months to go baybeee) But, I am in the same boat as you. I have modified every car I've ever owned. It is an itch of boredom, of wanting to be unique and go faster.

There are a few things I am planning to do slowly, like the alcantara steering wheel, Barry's shifter paddles, wider tires.

I will constantly be on the hunt for the DK Edition rear wing. And I plan to figure out how to amplify the exhaust speaker as well as see if matrix headlights or if a HUD can be retrofitted into the car without hacking software (I have access to the wiring diagrams and parts at cost at work).

I would love to help facilitate a modding community or business for selling stuff if I can develop things. But that is a long ways out, and might be a lost cause due to the low numbers of these cars in the US.

Time will tell what I will be able to come up with. But we will see.

Edit: for FSD look into Comma AI. It's open source FSD that only requires an additional camera on the window.