When I say he’s gotta be iconic, I mean from the audience’s point of view, on a scale of how legendary a character is. Someone who is the major hero in their story that’s known by everyone the world over. Someone who, you say their name, and everyone instantly recognises them as one of the major stars of the story. You say “Evil Queen” and it instantly conjures up a larger than life mental image. She should be paired with someone who people think of like that. To put her with a lesser character, would give the pairing an unbalanced perception for the audience.
I agree Regina’s love interest needs to be iconic in his own right. Eric would fit the bill. He’s not “big” per se but everyone recognises him.