My 525 build as an "Adventure bike" is on here.
If you are asking what modifications to do, these would be mine.
Seat, bars, pegs, grips. You are going to be in contact with these for a long time, make sure you are comfortable sitting, standing and all points in between.
Tank. Most fuel range you can manage. Mine will get 200 miles, haven't tried any more than that.
Luggage. Smaller bikes have less capacity for luggage. Make sure what you need to take fits on, and doesn't interfere with riding the thing.
After that, the discussion about what is and isn't essential gets a little blurred.
More oil capacity, or more oil changes?
Cush drive or gentle throttle?
Better lights, or don't ride in the dark?
Better electrics for gadgets, or a handful of AA's?
Etc,
Good luck.
Mark
Just read it, great read.