The seat, you can decide for yourself.
As to ‘Must have’ things? The only things I have added that are truly useful are:
A. A short male to female extension lead, that plugs into the very awkward USB socket on the upper right of the dash. That though has become redundant as I have now converted my tank bag to have a power socket.
B. A short right angled Hella plug to go into the power socket on the upper left of the dash. It didn’t have to be right angled, I just thought it looked neater. This I connected to a three-headed female DC power lead to power:
1. My tank bag, see A above.
2. The remote temperature controller for my electric jacket.
3. One spare.
https://www.ukgser.com/forums/showthread.php/570382-12-volt-power-supply-upper-left-cockpit
C. A piece of Velcro on top of the front brake reservoir, to hold the remote temperature controller for my electric jacket in place. See B 2 above.
D. A flying lead, exiting underneath the seat on the near side, to power my electric clothing and, if necessary, to power my tyre compressor.
E. The BMW ConnectedDrive Cradle, to carry and power my phone. This is only because I am using the BMW ConnectedDrive navigation app, along with testing the beta version on behalf of BMW.
F. The BMW Emergency Services bar, which fits above the TFT screen, to carry my Garmin XT navigation device. I am running the XT simply as a back-up to the ConnectedDrive app.
https://www.ukgser.com/forums/showt...S-Adventure-Relocate-sat-nav-mount’s-position
G. A third party support, to carry the mount for my XT on the Emergency Services bar, simply as the Garmin supplied Ram Arm support is horrible.
https://www.ukgser.com/forums/showthread.php/577855-850-GSA-Emergency-services-bar-Ram-Mount-and-XT
H. Inserts into the sharks teeth footrests, simply to stop the teeth cutting into my Daytona boots’ soles, which are quite soft.
https://www.ukgser.com/forums/showt...-Rubber-inserts-for-the-shark-tooth-footrests
I have added nothing more, nor do I intend to. Will the bike work perfectly well without any of these things? Yes, of course it will. They are just bits that were useful to me. Others will no doubt recommend all sorts of bling, up to and including: Screens, reservoir guards, cameras, bar risers, different hand guards, adjustable levers, muffs, assorted tank bags, different panniers / soft luggage, tyres and, ultimately, dust caps. They are welcome to it all.