Sorry for this bit of thread spirit singing, but it was close to the top of the listed threads, and the harlie forum is a tad on the slow side so...
For troops in an eldar codex harlequins list, I'd say that bikes would work just fine. Give them a warlock with enhance to make them *slightly* more harlie-like in close combat. Rangers work as mimes refluffed as snipers, or you can even use them as an (extremely overpriced) outflanking objective grabber or emergency assault unit or something. Granted, that's highly inadvisable. Storm Guardians with an enhance warlock sorta works, but I don't really care for that option. Still, totally doable.
Alternatively, you could consider doing the same thing but with the dark eldar codex. Run a wych cult army to get lots of lithe, double close-combat wielding elves who "dance" out of the way of danger in close combat. They also have bikes if you want them as well as open-topped vehicles.