I think all of her spirits technically have the ability to open their own gates, they're just not strong enough. Loke is the strongest (he is the leader, after all) and I'd assume that all of her spirits, given enough training, could do it too.
Horolgium the Clock does it as well, when he senses that Lucy is in critical danger and might die. (He's the one that saved her from turning into Lacrima during the Edolas arc.)
Actually, I think they all summoned themselves when she managed to summon the Celestial King to plead Loke's case.
That's actually an idea I've been meaning to explore in a fanfic. I want to see all of the summons get powered up. We know they can change their forms depending on the summoner's will (Virgo went from a fat lady to a young girl), but I'd also like to see them evolve. Like Pokémon.
And everyone has a final form that is like, super epic. Like Aries turns into a super badass fireball of doom.
As for the manga turning away from Loke/Lucy, it comes down to it being an unequal relationship. It's master/servant , mortal/immortal, ancient/teenaged.... Loke loves Lucy, and she loves him but she also loves all her avatars. Loke may very well be the closest out of all of them, and her favorite, but in the end, their love would be destined for tragedy. I believe Lucy figured this out even after she dismissed him due to his playboyness. Maybe allowed herself a teeny crush but forced herself to get over it fast.
Loke/Aries has none of those problems. They're both immortal, both of the Celestial realm, both the same age, and both servants to the same master.
I dont think lucy Loved Loke ever.. she did blush now and again when Loke tried it on with her and shows she cares for him deeply but not love. Loke loves(d) Lucy but it never went anywhere.
Lucy doesnt have Pieces or Libra spirits yet.















