I don't see the point of encrypting a wallet.

How strong is your encryption key (pass phrase) going to be?

If it's short enough to be easy to enter every time you want to spend bitcoins (like a PIN), an attacker who's got your encrypted wallet data can brute force it in seconds on a home PC.  The strength of PIN-based protection is in the app, which restricts the frequency and number of PIN entry attempts in order to thwart brute force attacks.  As an encryption key, it is useless.

If your pass phrase is long enough to be secure, do you really want to type it in every time you need it?  You will have it written down on a piece of paper, because a long, random and rarely used secret is easy to forget.  Then someone will request a feature to scan the pass phrase from a QR code.  And then you will realise that something like that already exists in many wallets including Mycelium, and is called cold storage.

Cold storage is simpler and more secure than encryption.