If you are going to do additions (bourbon, banana, etc.); you might want to offer him a few variations... a sampler pack so to speak. Make one with just the core/basic concentrates, a second with core + bourbon, core +banana, core +bourbon and banana.
If you give him just one "blinged out," everything-and-the-kitchen-sink, and he doesn't like one element; he could write off an otherwise successful mix. Just something to consider.
When you mentioned pecans and creams, I immediately thought of
Wonder Flavours Roasted Pecans & Cream. A while back, there were several folks on this
thread, who were raving about this one as a stand-alone winner. This might give you the nut and cream elements you seek; and only need a light tweak on the caramel.
I haven't tried it yet, myself; but all the ravings got me to put it on my list. I will have it when last weekend's BCF order arrives.