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:
Here it is in action - I took a fresh wallet and imported both the general and bounty donation addresses as part of an exercise prompted by remembering to demonstrate that the original QRCode image generation facility still works as expected with watch-only addresses:

and I can take the opportunity to expose the ugly reality of the UI presentation:

And when the watch-only txs are admixed with the ordinary-but-indistinguishable tx associated with one's own addresses, it becomes a right dog's breakfast. Aaaand the tx date is incorrectly shown in the listing - which is why a separate listing will be required for txs associated with watch-only addresses
If I can find a single point in the stake-calculating code which can be used to filter out watch-only addresses from the rest (any address without a privkey is a watch-only address)
and I can persuade the wallet to filter out the watch-only txs from the overview
and I can create a duplicate of the tx listing that is specialised to watch-only addresses
then we could be in business.
Cheers
Graham