Ok, Could I take any ROM as my 'port ROM' or is it supposed to be device specific? Could I take a Ressurection Remix ROM based on mm which was ported to my device by someone else as my base and Lineage OS 14.1 (of any device) as my 'port'?
You've done it! Now all we have to do is to make it into a flashable ZIP. Pay close Attention!
SELECT META-INF, system,file_contexts(if it is one) boot.img, data(if it is one).
Right Click and Select Add to Archive..
Select the Zip button.
Type the Name (Don't delete ".zip" at the end).
Click OK when ready..