+ Full web api, to administrate your wallet remotely as you said, easily from a web page. Security is a concern, so I would limit what it can be done.
+ The web api would allow you to do integrate with a web wallet, you could use angularjs and even "reuse" the code from the main wallet.
+ A restricted web api can be used for security, adding an extra barrier to break to get into the wallet.
+ The service can be used as the generic interface class for anything
(An Exchange, a bot, e-commerce)
Mainly you have .net and bitshares the world is your oyster. (same as nodejs, python, c++ )
Just make your life easier and make sure is portable (mono, linux)