@basic, being in the same city as you, your post has inspired me to get GS 150, so I am getting one next weekend. I want add mods like rims, disk break or at least the fuel gauge. 
Since the local mechanics that I know are either incompetent, thugs or incapable to understanding basic human language (if you know what I mean
), do you know if the guys at Suzuki service would add the mods for me if I buy and pay them to do so? And would they still honor the warranty?