This is hard needed. All the wallets are driving me nuts!
I don't know if QT wallets offer some kind of API system where they communicate commands within a system (non-tcp-ip). But then you could think of a proxy-wallet. A virtual wallet that needs the real wallet to function, but just helps in keeping everything manageable.
The reason I suggest this is because often wallets get updated to fix forks or issues like the 1doge minimum fee to prevent flooding the system. Effectively you also relay responsability for loss and hacking etc to the original wallets, not you. It would make development easier, I think, once past the stage where you have to figure out if you can communicate with individual wallets to provide VirtualWallet interface.
Also I think this would make updating existing wallets friendlier - your wallet could check for the latest version and notify a user.
I guess in a way I'm a bit inspired by MultiMiner and GUIminer, the first also notifying you of new updates (and downloading them upon user confirmation - great!).
Edit: Also perhaps running such wallets in a sandbox might be useful to prevent inter-wallet communication (in case of infected wallet download of some new Alt coin - I'm continuously worried about that).
The wallet, if I did my research right, does offer some kind of internal API, because the Qt wallet is just a GUI for bitcoind. When you say a "proxy-wallet", what you mean is the Qt wallet for the coin is directly downloaded to a special directory under the main Wallet's, to be used as a remote for manipulating altcoins? So the main Wallet would not hold coins, but would send commands to the right altcoin wallet? Tell me if I'm mistaken.
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Guac, if you use Skype add me. artw1982
Will do when I come home.