My Electrc-Picture-Maker is a D3200, one of the more compact DSLR's about. Curiousely it is MORE bulky than a lot of my old 35mm film cameras, and when I evicted a par of winder equipped OM's from the gadget bag to make space for it.... it filled it all! And that was without a battery grip! So it may be more compact, but its not THAT compact...
And I do have big hands! This is not really a issue I have with cameras... I DO with mobile telephones... especially ones with 'touch-screens'.. not so cameras!
The verdict is still'out' on the durability of the EPM.. I very much doubt it will prove as long lived as my 35mm film cameras, of which most are best part of 30 years old or more and still going strong! But I seriousely doubt that t will last that long, and experience of lap-top batteries suggests I'd be lucky to see much more than 3years from a battery for one, and pot luck whether when that dies replacements will actually be available!
On that score, the OEM vs After-Market battery question is not one that really bothers me too much; I have two genuine Nikon batteries and two after-market. I don't find swapping them a particular chore, nor particularly frequent one; certainly compared to the rechargeable AA's in the motor-winder for a 35mm film camera!
So, NO, I would not recommend a battery grip,particularly if at all.
YES, would recommend spare batteries!
Not a big problem on a film camera f the winder batteries die; they are AA's you can pick up a pack at a petrol station, or just use the manual advance lever! Button cells for the meter, are useful to have handy, but even there, not so essential... except on the battery eating OM4, but least said about that the better.... but even on that it can be fired on mechanical settings, if you neter with a battery-less celenium cell light meter or old fashioned f-16-sunny type estimation by eye!
Slightly bigger problem on an Electric-Picture-Maker... sort of rather useles if they run out of electric really!
And Murpheys law says if you only have one battery, it'll be flat when you need it.... if you have two, the 'spare' will probably be flat too, for thnking you were a bit smart, so you need at least three or four, in which case they will ALL be charged, so Murphy can laugh at your chagrin for 'wasting' all that money on batteries you ever use... but hey! At least you are taking pictures!
BUT Top-Tip...Memory-Cards. You can fill a card faster than you can flat a battery, and waste more time and more battery still, trying to parse out duffers on the card on the spot to squeeze a few more on it. Much better, and quicker and reliable to have spare cards... especially if you are 'away-from-base' and cant clear down so regularly.
I have three 16Gb cards for the EPM.. here bigger cards seem like a better option, but bigger cards are often slower and usually more expensive, and you are tempted to not clear them down so diligently and end up wiping shots or double down-loading. Good cards are a real BOON, and write speed is the most important spec on them, buy as FAST as you can afford and check specs carefully, they often try hide that they aren't as fast as they may be quoting 'average access speeds' inflated by a far higher access speed than write speed.
To wit; spare batteries for electric-Picture-Maker, as they are a small investment, and an electric-picture maker with no electric is a chocolate tea-pot! Spare memory cards, because if you do have electric, its o good unless it gives you pictures to take home!
After that? You can wast as much money as you can afford on Gadget Acquisition Syndrome...but, you only need a camera and one lens to take a picture, and in days of yore 'masters' did great work with very humble fixed lens, fixed focal length cameras and ls single exposure 'plate'! Modem entry-Level DSLR is almost every lens and every film the shop, in your hand... important thing s to know how to use it, and THAT you don't get in a cardboard box! Save your money to get out and about ad use the basic camera as is, and don't look at the brochures again until you are actually struggling with anything, AND you have gone done some research to eliminate the likelihood its lack of know-how causing it, not lack of gear!