So Currently Harpies are probably the worst species meta wise, they Unique features all lack any practical use, like mimic and flying or are an active weakness like breathing significantly faster and being super weak, being able to be just instantly picked up and not being able to escape when picked up.
Being so weak is actually one of the best things about Harpies aside from beings the Objectively cutest witch can not be argued.
Anyways I think it would be cool to make Harpies even more Fragile but offset that with unique strengths, basically make Harpies take significantly more blunt damage specifically to the limbs, but also im general, so being hurt more when hit, running in to peeps or running in to walls.
Having it be easier for them to brake bones.
To ballance, Harpies could have Birds eye toggle like binoculars witch you can still use guns, move fast or so do things well using.
Also tying in with the disadvantages, could make a stamina system for Harpies where Harpies have max higher stamina and stamina regeneration when health, but loose max stamina and regeneration speed as they brake bones.
Over all this would give Harpies a unique niche where they excel at ranged both for combat but also just threat detection, amd excellent mobility at the cost of being hopeless on the front line of danger as they are highly incentivized to avoid melee range at all costs as taking damage with significantly weaken and slow them. As it eats away ay their stamina.
This would essentially make Harpies snipers or scouts in combat roles, the polar opposite to Omni berserker role or Diona tank role, yell also differentiating from Rodentia assassins, thief or stuff, among other more fragile species.