It's possible that they could do Catwoman without the actual feline costume. She could simply be a skilled cat burglar, who wears a mask tight-fitting catsuit (as oppose to a Cat suit). Something like Catherine Zeta Jones in Entrapment. Or perhaps after the tabloids refer to the mystery 'Catwoman' thief, she starts wearing cat ears along with her mask and donning claws, to play up to the nickname. Just a possible way of distinguishing her from Michelle Pfeiffer's memorable take.
True, Selena Kyle and Harley Quinn sound like the most interesting choices, although the characters would have to be made more realistic.
Selena, as shown in the previous film and TV versions, was too much of a parody. If they toned down the cat element and made her more of the ultimate cat burglar with a complex personality and possibly a background in gymnastics there's a good chance it'll work.
Same with Harley, who'd be a lot more interesting if they toned down the lunacy and mixed her personality with the version from Birds of Prey
. An extremely intelligent and resourceful woman who was drawn to and fell in love with a maniac and over time she went off the deep end as well. A former psychologist or policewoman who now uses those skills to her advantage.