Can I reuse blockchain/index files with multiple wallets?
You can swap wallets around and synchronise them up with the same block chain data files - you would just need to replace the wallet.dat files in the Bitcoin's data directory. The client would only synchronise once with the network and later be able to synchronise your wallet files independently. Keeping up with which wallet is synchronised and which isn't might be a bit of a hassle though. I don't know of a client that can operate multiple wallet.dat files simultaneously.