Well, the problem of Nikon bodies is that there is ususally a space for the battery or the capacitor for the integrated flash in the grip. The latter is about the size of an AA or AAA battery which is pretty large. It should be difficult to make the grip to be interchangeable.
I'm not sure I understand your concern, from an industrial design perspective. I'm not arguing for the removal or interchangeability of an existing grip. Rather for adding something to it to attain the desired result; ease of handling. If should be relatively simple to sheathe the grip in some manner, effectively making it thicker as needed.
If not for concerns regarding voiding warranties and such, I could handily solve this problem for myself. At the very least, there are any number of industrial grade adhesive-backed rubber strips that can be
applied to add some girth to a grip. (Say that, five times fast!) In fact, I used to appropriate
surplus rubber strips like those mentioned, from a factory I worked in, for the purpose of protecting the bottom plates on my F & F2 from the results of rough handling in the field. Worked at treat, too! They were flexible and easily cut; conformed to the contours of whatever apparatus they were applied; relatively impervious to the elements (they had a military "spec" rating) and could be removed cleanly if necessitated.
What I wouldn't want to do right off is risk sinking the bit of a Dremel™ tool into a fully charged capacitor, as I drill a hole, or two (I should live so long) into a camera for the purpose of affixing an auxiliary grip. Even drilling into an exhausted, or discharged, capacitor would be unwise if I had hope of maintaining a fully functioning camera. I wouldn't -- in fact I don't -- recommend anyone try it. Let Nikon think it through and come up with a better design scheme -- next time!
