Well as Kiwi recommended, started toying around with plugboards and they are very convenient.
However i don't think even with plugboards i'll find a way to reconcile Metadata/Filename/GenerateCover.
I'm going to keep trying to make a RE for GenerateCover saying ""pick the title, but when you see a minus sign, delete it and skip one line".
Spoiler:
My regular expression tries to add series index (an extra problem to deal with) and i'm still stuck with the "minus sign" in the covers for extra long series...
Using the best RE i could come up with :
(?P<author>((?!\s-\s).)*)\s-(?:\s(?P<series>((?!\s-s).)*)\s-)?\s(?P<title>.*)
With < John Doe - End Of Time 1 - The Start.epub > I get
Authors : John Doe (Perfect)
Series : End Of Time 1 [1] (great now i have a [1] to get rid of)
Title : The Start (Perfect)
With < John Doe - The Ever War - First Years 1 - Alex Smith.epub > i get
Authors : John Doe (Perfect)
Series : The Ever War - First Years 1 [1] (damn that [1] is here )
Title : Alex Smith (Perfect)
Assuming i could find a way to remove the index (tried but failed) i would end up with :
Authors : John Doe (Perfect)
Series : The Ever War - First Years 1 (no index, just pure text values)
Title : Alex Smith (Perfect)
So far so good, but when you get to the Cover Generation the problem i had with the minus is still present.
I'll still end up getting :
The Ever War -
First Years 1 - Alex
Smith
Instead of
The Ever War
First Years 1
Alex Smith