Neat lineart designs, although I'm not sure what design you're trying to go for with this hoverboard user. When I hear hoverboard I think of skateboards and skater punks/skater girls, and I don't get that impression from her in these designs. What does she use her hoverboard for? Does she have a profession? Does she work for an organisation? Is she a lone wolf? Is she a fighter? An engineer?
What exactly is the robot's purpose? Is he like a sentry robot? I read that he transforms into a powersuit for tricky situations, but what are they? Are they for fighting the enemy? Handling heavy duty tasks? To help travel in inhospitable environments?
Sorry I sound like a badgering critic. I can see you've got ideas for your character but I'm not sure how the character, hoverboard and robot connect together as one cohesive character. (Not yet anyway.)
Out of the 3 female designs you have here, the middle one looks the most interesting, but maybe trim off the skirt? So she has a body suit like the first design?
Hope I wasn't harsh, it's all my own opinion. Good luck with your character.