iPhone 6/6s Smart Battery Case Mini-jack (3.5 mm) input hole expansion

It was difficult to tell, based on the breakdown of the Smart Battery Case (for iPhone 6/6S) whether or not there was room to delicately sand/drill/or otherwise manipulate the case to expand the hole in the Smart Battery Case. The purpose being to allow for plugs (even slightly) larger than the original Apple EarPods Earbud Earphones with Mic mini-jack plug?

I don't want to break the device, and I'm too concerned about voiding the warranty (if one exists on the item), however, it is nearly unusable with any cables/cords other than the original Apple ones.

Any and all help would be appreciated!