Just joined this forum and saw this topic, so my apologies for being late to the conversation. I have a 2014 i3 BEV. Here're the things I did as minor "mods" to make it more user friendly to me.
1. Horn addition - the i3 somehow comes with only 1 horn while other BMWs come with 2 (Hi/Lo). So I added the missing one (just the 500hz one)
https://www.amazon.com/85110-115db-400HZ-500HZ-Sports/dp/B00067BWBI. (Difficulty level: 3/5)
2. LED high beams and front turn signals - my 2014 model came with incandescent bulbs for the highbeam and front turn signal. Easy swap with LEDs from Amazon. Took me 2 tries to get the correct amber LED bulb that gives enough forward illumination to work well. I got these
https://www.amazon.com/gp/product/B07BF3SRP1. The highbeams were easier, just get a good H11 LED headlight bulb. High beams are so much better now than the mediocre incandescent ones - really surprised BMW let this one slip. (Difficulty level: 2/5)
3. JBL BassPro SL 2 subwoofer - even though my i3 has "Harman Kardon" system. It's missing a sub. Probably for "efficiency" reasons. So I added this thin one
https://www.crutchfield.com/S-ojunx3nUIpp/p_109BASPRO2/JBL-BassPro-SL-2.html leaning on the left side of my trunk. Wired it into the head unit wires under the rear seat. (Difficulty level: 4/5)
4. BMW auto-dim side mirrors with (Euro) blind spot outside section
https://www.ebay.com/itm/BMW-3-F20-...G-HEATED-MIRROR-GLASS-RIGHT-OEM/202897806604? - my i3 was supposed to be "loaded" US spec, but it only had 1 dimming side mirror, and no blind spot section. Since this car has no electronic blind spot monitor, adding an original BMW Euro blind spot mirror really helped. So I got a pair from eBay. Waiting for them to be available proved more difficult than the install - which was straight-forward 15-minute job. The car's already pre-wired for it! (Difficulty level: 2/5)
5. LED ribbon trunk light - with only 1 side mounted LED bulb for the trunk, it wasn't really lighting up the trunk much. So a cheap white LED ribbon
https://www.amazon.com/gp/product/B07V6CXWDK, stuck underneath the parcel shelf hidden from view made it much more usable at night. Wiring was so simple I only needed to pop out the original trunk light to make a parallel connection using one of these
https://www.amazon.com/gp/product/B0054D80LE via the existing holes on the side of the trunk. (Difficulty level: 2/5)
6. Custom car-specific magnetic phone mount - I hate wires, I hate having a bulky thing sticking on my dash, and I hate having any clip on mounts blocking my AC vent. Cup mounts also didn't work for me because I need my cupholders! So I got a ProClip USA vehicle specific mount that clips on to just BELOW the AC vent and the power socket
https://www.proclipusa.com/vehicle/dashboard-mounts/9622-bmw-i3/2014, and added a big stick on magnetic mount
https://www.amazon.com/WizGear-Rectangle-Dashboard-Swift-Snap-Technology/dp/B0756NFMCC on it. So my phone will mount in landscape position right below the vents, and even has a short USB C cord plugged to the power socket. With the phone on the mount, you CANNOT see the mount. It's like your phone was part of the lower dash. I also got these awesome Aukey PD/QC 3.0 micro car phone charger that "disappears" into the power socket. (Difficulty level: 1/5)
7. Front/rear dashcams - I got an Aukey DR02
https://www.amazon.com/gp/product/B075S7W6FR, along with their AUKEY Dash Cam Hardwire Kit with Motion Detection Sensor
https://www.amazon.com/AUKEY-Hardwire-Detection-Dashboard-Cameras/dp/B07J3BLFBN. For dashcam as well as surveillance duty. (Difficulty level: 3/5)
So I guess these mods are more for safety, security, and comfort categories.