ArniA:
Perhaps both titles should be displayed on MDL.
In the case of Koi wa Tsuzuku yo Doko Made mo, it could be displayed as a sub-title something like this:
Koi wa Tsuzuku yo Doko Made mo
(Love Lasts Forever)
Your example makes sense in terms of how it should be displayed...but it would need a CSS design re-consideration to have that 2 lines on an HTML page. Knowing that not all Japanese drama has English title and other dramas only use 1 line of title, the MDL website would easily look inconsistent....this is just my personal opinion...and I am not a web developer though..
I guess, the current system is the best, where you have the "also known as" section that can contain any other aliases for a particular drama. Most importantly, these aliases are searchable (not sure if it really is but it should be) so it won't be a problem for a person who is searching for any drama.