Adaptive cruise control is one of several options included in the Technology + Driver Assist package. Automatic wipers might be standard on all i3's. I would not be as happy driving an i3 without this package.
The only other available package is the Parking Assist package. The backup camera and front ultrasonic short-range sensors are the only features of this rather expensive package that I value. The self-parking feature is slow and has curbed too many wheels to be of value.
An individual option is the Harman Kardon sound system. If you really value high-fidelity sound, this is superior to the base sound system although it apparently lacks strong bass, but it was not worth $800 to me.
Another option is 20" wheels. Only summer tires are available in 20", so if you might need winter tires, you'd need to buy a set of 19" wheels as well. The standard 19" wheels are equipped with all-season tires which apparently provide a more comfortable ride than the low-profile 20" tires.
Any paint color than white is apparently an extra-cost option (~$550?). An optional paint color wasn't worth that much to me.
Some other features are bundled with trim packages. The basic trim package is Deka World which was not a trim package available when we bought our i3, so I'm not familiar with it. I think it has cloth seats and does not include some of the interior and exterior LED lights included on higher trim packages. It might not include LED low-beam headlights which I would want. All 19" wheel options might not be included with Deka World.
Mega World was the base trim level when we bought our i3. It has light-colored cloth and leatherette seats (BMW wouldn't call it "leatherette"). It used to have very light carpets as well which show dirt easily. It did not include Comfort Access (unlock/lock without using the fob) in the past, but it might include it now. I would not want an i3 without Comfort Access. LED low-beam headlights are included.
Giga World includes tan leather and gray wool seats and a wood-trimmed dash. That's what we bought. It is a very attractive interior, but its light leather-covered steering wheel shows dirt. Cleaning it can unfortunately remove the light paint on the leather (yes, the leather steering wheel cover is painted). It has a full set of interior and exterior LEDʻs including low-beam headlights. Comfort Access and a built-in universal garage door opener are included.
The top trim level is Tera World which includes everything in Giga World but has full leather seats and a dark leather steering wheel cover. Compared with Giga World, the Tera World interior is too dark for me. Also, leather in our warm, humid climate isnʻt as comfortable as cloth.