This version will introduce a new version of the cipher format, possibly with a JSON or XML header. This will allow following improvements:

• We can differentiate between password- and key- encrypted ciphers
• Only fields that are needed can be saved: a key-encrypted cipher does not need password salt
• It is prettier.
• I'll have to rewrite the terrible code which handles encrypting & decrypting -> prettier code

Will it be more efficient? No. But it will be easier to debug and understand. That is worth the extra very few bytes. Parsing the header from XML/JSON will still be secure, HMAC protection will remain unchanged.

In this version, the target .NET version will be 4.6