Seeing as Hefeweizen is kind of 60% Wheat & 40% Lager with just a bittering addition, is it really going to matter which bittering hops you use?
Could, Bobek, Herkules, Pilot, First Gold, WGV, Willamette, Target, Bramling Cross, Progress or Admiral do the job just as well... is the general Hersbrucker hop flavour in a Hefe hidden behind the yeast character and the full boil??
I'd say that your assumption is correct. Bittering hops do give some flavour but at the EBU's required for a bavarian style wheat beer you would probably be fairly safe using any hop you liked. I would go for it...
bobek woud be lovely - a little more belgian maybe but should citrussy / spiciness should complement it really well. (May have to try that myself - used them in my witbier)
Willamette as mittelfruh descendent would be good too which Aleman suggests - I'd go low alpha though rather than high so you get a little bit of a hop bed and no harshness.