DE Allies ? stick 5 in a venom or 10 in a raider ? - you do need a support unit if the target is in cover though - mb some cheap quins, or even scorpz. [ to take casualties so banshees can get in]
on a design note - how crazy is it that they get a 3" run bonus - but not on the charge !
and the no grenades issue is so easy to resolve - just put a bit extra on the mask "when a model wearing a banshee mask charges into close combat it ALWAYS strikes at I10" ...
im going to roll my next eldar game with a 'quin-suprise' - just for a giggle. two sets of quins with a mounted farseer per unit. not sure if i shopuld run them on foot or pinch some raiders for mobility! might stick two de units in the army anyway just for the option!