How about an option to allow the Bitcoin to run in Heavy, Thin, or Lite mode?
Heavy, having the whole blockchain downloaded.
Thin, having only your transaction (sent and from) addresses shown.
Lite, using someone else's blockchain to verify payments. (
http://ecdsa.org/electrum/ )
These could be modules that would be required to restart the client before the module would be activated.
There could also be an option for cross-verification with 2 or all 3 of these modules.
Just an idea...