Interesting experiment! It's always fun to experiment with new tastes.
I contend, however, that you're never going to be able to tell the flavor contributions with all of those specialty malts in the grist, much less all those spices. Don't get me wrong - I think the beer will be fantastic as written! All I'm saying is that if you're looking to explore what impact palm sugar will have on beer, you must seek simplicity in the ingredients.
Pick ingredients with which you're very comfortable and familiar, the flavors of which you know you can identify. That's the only reliable way to tell - if you can say, "Okay, that flavor is the Maris Otter, this flavor is the Fuggles, the other flavor is the Windsor; so this out-of-place flavor must be from the sugar."
It's either that or brew a recipe you've brewed time and again, a recipe your taste buds know inside-out, where you know you'll be able to spot any difference, and add the odd ingredient to that.
But hey, I totally dig it if that's not what you're after! Like I said, your proposed recipe sounds like it comes from the whackjobs at Dogfish Head - and that's a compliment!