[Epic 4G Accessories] bitbang3r:
No, it should be based on the ActiveX (which has a padded "undercase", and fills in the button gaps to level out the sides and provide extra protection).

Here's how I'd do it:

Sku #1: ActiveXR Case. Start with the ActiveX, but score a cutout in the padded underbody above the battery's footprint. Include two exoskeletons: one that allows the keyboard to slide out, one that firmly secures it in place.

Sku #2: ActiveXR PowerPack, consisting of an extended battery, two backs, and a GameGripper that's customized to fit an Epic with ActiveXR case with the keyboard-openable exoskeleton in place. This battery might have to be smaller than 3000mAH, but should have at least 50% more real capacity than the Epic's stock battery. If the battery ends up being a hair too thick, make the padded underbody of the ActiveXR case a little bit thicker too.

Use Case #1: Extended Battery

Carefully cut out the scored rectangular opening on the ActiveXR's underbody with an X-acto knife. Save it for future use.

Remove the phone's stock back and battery. Insert the extended battery and the back with a cutout. Attach the padded underbody. Verify that the squishy thin adhesive-backed silicone pad is attached to the extended battery, and stick it on if this is the first time it's being used. Attach your exoskeleton of choice. Enjoy added battery life and added protection, with optionally-secured keyboard using exoskeleton #2. In both cases, the exoskeleton is what ultimately holds the extended battery in place.

Use Case #2: Gameplay

Same as before, but use the exoskeleton that permits the keyboard to open. Slide open the phone, attach the ActiveX PowerPack GameGripper, and have fun. This is a crucial part of the whole system. A "normal" GameGripper for the Epic (presumably) won't fit an Epic with ActiveX(R) case attached, and the case can't be removed because its exoskeleton is the only thing actually holding the extended battery in place.

Without the ActiveX PowerPack's customized GameGripper, you'd have to remove the case, and carry BOTH the standard Epic GameGripper AND the extended-battery phone back that doesn't have a hole cut into it. Yuck. Have I made it clear yet just how important the availability of a GameGripper that can work with the ActiveX(R) case in place really is?

If the user has the openable exoskeleton attached, all he needs to carry in his other pocket is the GameGripper.

Compare that to the nasty alternative that pretty much kills the user's ability to whip it out for a couple of minutes of casual gameplay while waiting in line somewhere: Shut down the phone. Remove the exoskeleton. Remove the ActiveXR's back. Remove the battery back. Remove the extended battery. Put the stock battery into the phone. Attach the stock battery back. Power up the phone. Slide out the keyboard. Attach the standard Epic GameGripper. It's a well-worn cliche, but apt: "Epic Fail" -- too much work and hassle for too little reward.

Use Case #3: stock battery

Insert the stock battery, and attach the phone's stock battery back. Attach the ActiveX(R) underbody, and stick the rectangular cutout into the cavity. Attach either exoskeleton (securing the cutout into place, and hiding the fact that it was cut out to begin with).

Target Market for ActiveXR PowerPack: users who push their phones to the limit and would kill a stock battery in 4-6 hours, and probably play games (many as a prime activity, plus others who wouldn't really go out of their way to do it, but will take advantage of the bundled GameGripper if they had to buy it anyway to get the exteneded battery). These are users who don't really mind a thicker-than-normal phone and urgently need more battery life, but would balk and be unhappy if it made their already-thickened phone even thicker... and will happily trade padding for more battery.

Another argument for Seidio: competition for cheap batteries and cases from eBay is stiff... but none of them will work with an Epic GameGripper. The guy who makes the GameGripper sells it for $15, so it's probably pretty cheap to make. If Seidio offered to buy 10,000 from him that were customized to fit a phone with ActiveXR case for $1-2 more than he pays to have them made, and most were bought by users who couldn't easily have used a stock GameGripper with their ActiveXR-equipped Epic *anyway*, he'd be insane to say "no". Especially if, say, Seidio also became a dealer for them in general. ;)