I think it would be a nice feature that any user can create offline address with their mnemonic passphrase (as paper wallet style) and add in the client as "only read" (like omniwallet) in order to control their funds and if later they need move their coin could add the passphrase in order to get private key for signing tx.
It's funny you should mention that. I found this gist lurking on github:
https://gist.github.com/WyseNynja/8120948It's a distillation of laanwj's bitcoin commit that implements just such a beast and at first glance, it does seem logical to embrace that power-up for wallet users. Unfortunately, the transactions associated with watch-only addresses would need to be explicitly prevented from being considered in stake calculations - which is a whole other ball game.
Cheers
Graham