Your app store will be like google play and apple store? where anyone can launch his decentralized app just like ethreuem platform or this is something different. Do you have any protocol to check whether app is legtimate to has some bug inside it.
Taking forward the idea of etherum is a good approach in my opinion. Ethereum has its own issues like increase gas prices during high traffic. If someone can come up with a fix to ethereum blockchain then it will defiantly receive lots of attention from the community.
I am still not sure whether Ethereum is full decentralized or not since it has a founder (who must have all details of how to manipulate the project). If there is any new platform launched with intention of providing a platform where decentralized apps will be hosted, it will defiantly have a moon short.