I made a couple 10 gal batches of a very neutral pale ale this past summer (2-row, carapils, cascades) to experimented with tinctures (I wanted flavorful beers on the quick for a festival). One utilized a masala vodka tincture that I added at kegging/bottling. The tincture was made by soaking the whole spices used in masala in vodka for two weeks. It turned out quite tasty and will definitely do it again. However, a couple notes I had were that the masala flavor dissipated more than expected over the two weeks it was in the keg (I'm going to muddle the spices and add in secondary to let the alcohol in the beer extract the flavor over a month period of time). Also, I feel a lager is better suited for this kind of flavor (it would allow that hint of masala to come through a bit more - i made the PA around 30ibus and even then I felt the hops overpowered the masala). Thus, if I were you making an IPA of this type, I'd keep it on the lower end of an IPA's IBU profile and perhaps add some masala in the boil as well as in secondary.
NOTE: I made a thai curry beer in much this same way, but in addition to a thai tincture, I threw a hop bag with the spices and herbs that had soaked in the vodka in the keg as well. It had a stronger, more pronounced flavor, and I learned lemon grass is a great beer ingredient!