Personally, even stock my 1150 Adv had plenty of poke but it was just too quiet. Now, with a light Y-piece made up to a Termignoni exhaust-can the quiet part is fixed (and how!) but the largest improvement was in the effect of losing all that weight of the standard parts.
Mods might make it look prettier (so to speak) or add a degree of pride, having put your personal touch to it, or more focussed on the sort of riding you do with baggage or whatever.
But in my opinion; performance wise the 1150, and especially the 1200, don't need fettling. It'll keep the sport bike riders honest and it goes alright for the whale that it is when off road.