At my cloud, your wallet will be hosted in your own Virtual Machine Instance, entirely encrypted with your password, which I don't know.
You need a light client like Electrum if you want to be able to scale https://bitcointalksearch.org/topic/announce-electrum-lightweight-bitcoin-client-50936.
Not if I use some kind of deduplication file system.
Also, I'm planning to create a feature called "download wallet", so you'll be able to open it in your own regular Bitcoin client.