What if i told you that that method already exists?
Try dek.im/arena. If you have Chrome the TL;DR version is the following:
1. Open your game and go to the main menu.
2. In the Chrome menu (which can be found in the upper right corner) go in Tools/Developer Tools (the keyboard shortcut for me is Ctrl+Shift+I)
3. In the pop-up table, click on the 'Network' tab
4. Open Arena. This will make a new item called T503 pop up. Click it. (if you have other tabs given there, click 'Preview', if not, then go to step 5)
5. Copy the full text that is shown in the minitable.
6. Open dek.im/arena in a new tab and paste the code in the corresponding box.
7. Generate deck code and forum code. Profit!