Good points, but I think that with some practice in teamwork of the sort employed in Neville's "Special Attacks," they could have come up with something. Say, Draco levitating Hermione horizontally out the window, so she can use a Shield Charm to cover herself completely while Draco moves her out of Harry's one-handed firing arc. Throw in a baseball-style hand-signal code between them, so if Harry is concentrating on Hermione, Draco lets her go while she casts Leviosa on herself, and he zaps Harry, or if Harry tries to take aim at Draco, Hermione drops her shield charm and fires. And this assumes that neither of them (or Genius!Harry himself, for that matter) can come up with a better flying spell than Wingardiam Leviosa.

Maybe their problem is that they weren't quite ready for that level of teamwork, though if it was me in either of their places I'd have wanted to look into developing an inventory of "Special Attack" type maneuvers after seeing them work so well for Chaos.

OTOH, the likely real reason is that the Gecko Gloves give Harry a chance to use Science! in a fun way, so the Rule of Cool applies. Still, reactionless flight is such a trivial matter in the Potterverse that I still found myself wondering why they just went out after Harry on his own terms instead of trying to wield air power against him somehow. Maybe a couple lines of dialogue along the lines of "Why don't we use [flight-based attack X]?" "We can't because Harry would just use an Indra's Net Jinx!" (or some other expected counter that makes using the Gecko Gloves then sliding around on the slippery roof their best response to the situation).