I recently had similar goals described by the OP, i.e., a "sessionable" IPA that emphasizes flavor and aroma, or an Extra Pale Ale (XPA). I found success with using BeerSmith and shooting for the very low end of the style guidelines for OG, IBU's, and ABV, while keeping FG and ABV in the low-average range.
Due to higher hop charges needed, I found more bitterness than I would like if I did all late hopping (including aroma steeping at or past knockout)--I think the reason for this is that IBU's continue to get extracted when wort temps are elevated (albiet slowly). I do 10 gallon batches and use a 50 ft IC. Your experience may be different with other batch sizes/methods.
I would stick with a small amount of high AA hops (e.g., Magnum) with clean bittering and focus more on small additions of the Cascade hops from 40 minutes down to knockout to get the flavor complexity.
Aroma hopping can be achieved with aroma steeping and/or dry hopping. I find aroma steeping to be cleaner and more subtle (yet approachable--it appeals to a wider audience of non-craft beer drinkers), while dry hopping gives us craft beer drinkers the "Wow!" we're looking for--however, the higher aroma levels often comes accompanied by grassy flavor and aroma notes that many non-craft beer drinkers struggle with initially). I find dry hopping's flavor/mouthfeel contributions seem to heighten my perception of hop bitterness and lessen my perception of the malt and hop flavor contributions. YMMV.
Try a split batch and only dry hop one keg to see which way you'd like it personally.