Yes. Exactly this. The Ethereal give your FW some Ld staying power, and a bunch of useful powers to boost them, two things they exactly need.
Another thing I suppose you could take is the Aegis Defence Line. That would give the FW a bit more staying power, another important thing, as those 3 scoring units will actually bear a lot of brunt for the sheer fact that they're scoring.
I'll here say that I agree with most of Wyddr's suggestion - any could work.
As a little side note: this is a personal preference, but when using broadsides as an AA unit, I'd switch out their Heavy Railguns for the High-Velocity Missile Pods. Usually, these fare much better against flyers, and IMHO, against all things.
Also: are you using Forgeworld models(ignore this comment if you aren't)? If so, I'd suggest taking a tetra squad or two. They're sort of like pathfinders-in-a-vehicle - basically, a tau vehicle primarily designed to markerlight opponents. It's two tetra's for 70 points, so they're not that expensive. (Their rules are in the new Imperial Armour: The Tauros Campaign, Second Edition.)