I hope the bitcoin-client can be developed in a light-version so you dont need to have ALL the blockchain, just the latest parts.
Centralized mining is more understandable, but thats also aginst the ideology of bitcoin.
Adam3us is warning about the centralization of mining in this thread:
https://bitcointalk.org/index.php?topic=180020I agree with you on a "speedier blockchain." It's painful to download and store the whole chain (~10GB now). Even harder to do it on a mobile device.
But I don't yet know how your proposal could be implemented easily, considering that all account balances have to be deduced from historical transactions in blockchain. I haven't read the blockchain pruning techniques proposed by Satoshi though.