Similarities between the two:
• They both were blinded by revenge and hatred at some point and sought for it even at the cost of their own lives (Deliora and Jellal) showing coldness and lack of basic human emotions.• Lyon (Before the Gruvion thing) was shown to be this cool-headed guy rivaling Gray and a fearsome individual to say the least. The same applies to Kagura who was shown first to be a calm, little word person who fought for her guild and was equally fearsome.
• Both of them were sorted and shown to the light by a person very close to them since childhood (Gray and Erza respectively) changing the course of their lives.
• The fact that Lyon is the older disciple to Gray and Erza acting more of a big sister towards Kagura isn’t much to talk about but it could count for a contributing factor?• They both lost someone very dear to them (Ur and Simon respectively) Which was the reason of their hatred and cause of agony.
• They’re both almost the same age as it’s shown that Kagura is a couple of years younger than Erza who was 19 in her debut which makes Kagura 16-17 during that period, adding the timeskips she’d be 24-25 right now where Lyon is 27.
• The fact that they actually interacted in both manga and anime makes it even more logical and more appealing to me at least.
Well I said my opinion and I this only came to me recently after watching Fairy Tail a second time. Besides, the fact that Lyon may want a rematch could make their encounters more likely to happen.