USB Program app development - For use with Television, via USB port

Sorry to burst your bubble, but in my opinion this would be practically impossible.

Your first problem is that every (or almost every) brand of TV runs a different way behind the scenes. LG, Samsung, and Panasonic all have HTML-based development, but each uses a proprietary SDK that are almost certainly incompatible. TEAC appears to use Android apps direct from the play store. Even considering that there are probably other manufacturers who just piggyback off Android and thus may be compatible with TEAC, you would still need multiple versions to support the major TV brands.

Second problem - many TV manufacturers require developers to pay a fee and/or accept a license agreement to develop for their product. Some are only to release it to their app store, but others require it before you can even access their SDK. Not a huge hurdle as such, but the more brands you support, the more you initially have to outlay.

Third problem, and probably the one that really kills your idea: Manufacturers generally require each app that passes through their app store to be checked for security issues and that they are of a professional enough quality to not reflect badly on the manufacturer, much like both Google and Apple do with their respective app stores. Why go to so much trouble with your own app store, just to then allow any random code off a USB drive to run? I would think running from an external drive would be blocked from most brands of TV due to the security risks involved for users and the liability it opens the manufacturer to.

That isn't all to say your idea doesn't have merit, just that you need to rethink the approach. The only way (in my opinion) to make your idea happen is to do it through each manufacturer's official method of development and release it through each manufacturer's app store.