iOS messages to iMessage (Mac)
This is possible. 

Move the sms.db and Attachments from your phone. They are located at /var/mobile/Library/SMS/ or you can extract them from a backup made by iTunes.

On your Mac, move the contents of ~/Library/Messages to a backup location. 

Copy the sms.db and Attachments folder to ~/Library/Messages

Using an SQLite browser such as DB Browser open the sms.db file and execute the following to change location of attachments:

UPDATE attachment
SET filename = replace(filename, '/Library/SMS/Attachments/', '/Library/Messages/Attachments/')
WHERE filename LIKE '%/Library/SMS/Attachments/%';

Rename sms.db to chat.db

Then you should delete the folder ~/Library/containers/com.apple.iChat and restart. You are now done.

Source: https://denbeke.be/blog/mac/exporting-messages-and-attachments-from-iphone-to-mac/