@MonsterFanfics_ Good evening (or good morning).
Thanks for your comments, I didn't expect your analysis to be so detailed.
First of all, I can't speak Spanish, it's just Google Translate. I wanted to save you the effort of translating (and after reading your comments, it seems I made the right decision.)
To be honest, I was planning to have Ulquiorra paired with certain characters: Mirajane, Merudy, Cana, Flare..; and sorry, Erza wasn't one of those chosen characters.
Your arguments and method are interesting, only an idiot would deny that. But let me clarify a few things:
1) The pairing between Erza and Jellal is good, I don't see the need to replace it.
2) In my story; Ulquiorra had feelings in the past, but, for some reason, he lost them and forgot about them (you'll understand after reading chapter 3 and 16). But let me tell you this, Ulquiorra's past is more complicated and sad than you expect.
3) I can't just split up a good couples just because I want the female character to be Ulquiorra's mate, and then leave the male character alone. That's unethical, even for fictional characters who don't exist in reality; I'm planning to pair Natsu with Lisanna, but that doesn't mean I'm leaving Lucy without a suitable mate. (Trust me, you'll be surprised when you find out who her future mate is. And as you progress through the story, even you'll admit that this pairing of Lucy with the unknown person is much better than Lucy and Natsu "Nalu")
4) Opposites attract. After a while of chapter 7, I noticed that the idea of pairing Ulquiorra with Cana was fun and interesting; a romantic comedy. But don't get me wrong, Cana also has hidden sides, but Hiro Mashima didn't touch on them enough, but I will.
5) In my story, I try to maintain a certain amount of logic so that readers don't see that I'm exaggerating some aspects of the story.
And Thank you for give me your time.