User blog comment:FairyRaven/Fairy Tail vs. Alvarez Empire! Place your bets!/@comment-180.191.134.131-20150916025154/@comment-7418318-20150916161730

Because of the danger of Elfman sacrificing himself to save Lisanna and the whole discussion about her being a burden starting all over again.

And because they'd serve the same combat role, so depending on the situation one of them could be redundant.

But if those two problems can be avoided, sure thing. :) Especially if Lisanna tries to get them to admit their feelings for each other. ^^