It can work. Just put more emphasis on gunplay rather than forming combos with swords and other melee options. Not only would it be new she will play drastically different than the other characters and as long as pro-Dante or pro-Nero players has their Dante and Nero (maybe even Vergil) I don't see no harm in using a character who plays by their own rules. Adds more depth and a new class of players into the mix (pro-Lady) so that people who mastered Nero or Dante will have to take time to master Lady.
Where she can switch between only guns or military based weapons ranging from pistols, shotguns, Kalina Ann, assault rifles, grenades (something Lucia used in DMC2), and more (satellite guns, laser guns, etc) and can use some basic hand to hand combat skills (like Trish or DmC Vergil or better Lucia when she does her various kicks).
Plus her main style could be the traditional acrobatic stuff in DMC2 but with more emphasis on acrobatics that Lady showcased in DMC3.
Plus her being human isn't a big deal I mean Ninja Gaiden chicks can take on demon emperors and whatnot and take a trashing plus Lady is no pushover I mean she got stabbed in the leg by a f*cking huge a$$ blade and kicked off a 100 feet tower and was later shown walking up said tower and even fought Dante although she lost and all of that was 10+ years ago.
Plus she is no ordinary human for she has the blood of a priestess (the same blood that can open and close the doorway to the underworld) flowing in her veins they can capitalize on that for a way to give Lady some reason to be able to give demons a trashing.
To balance it out and makes more sense due to Lady's greater range, strong focus on long range attacks, and her gun weapons do more damage than Dante and the others (but not DMC2 levels no those guns were overpowered) and having overall more usage she has lower durability so she takes more damage than the others adding a stronger sense of danger when playing as her.
