Yes, this is completely unnecessary but it will give one RP feature of Rift some functionality as well as levity.
1. Allow soul bound items to be exchanged with your marriage partner (given the item is appropriate for their class).
2. Shared marriage bank account.
3. Some kind of healing/damage buff when married couples are engaged in battle together.
4. Mounts made for two, for couples only.
5. Soul recall to your spouse's location.
6. Divorce needs to be fun: Best suggestions I've read:
a) A divorce arena for feuding couples.
b) for those that divorce you without notice, "if you divorce someone behind their back, you should automatically get a little lawyer guy attached to you that follows you everywhere and keeps asking you for money until you get the signature of your ex-spouse" (suggested by Cienn).
More suggestions please...