Here are some spec's I can contribute about the beer. I believe Vitus is considered to be a South German-Style Weizenbock/Weissbock - on the very pale end of the spectrum. Some specs from a great book about wheat beers...
OG: 1.068
FG: 1.009
ABV: 7.7%
SRM: 6
IBU: 17
Vitus has quite a high attenuation - about 86% - which I can see will be a bit of a challenge to clone. From what I've read Weihenstephan does decoction mashing in most of their brews. Unfortunately, I've never done any decoction mashing but their is a great article in Zymurgy (May/June 2010) on page 34 entitled, Brewing Wheat Beer with Intensive Banana Aroma, that really gets into how to utilize decoction to pinpoint the right kind of flavors and smells. From what I recall, Vitus has a big banana nose to it.
For a malt bill I would be thinking at least 50% wheat, with the rest being composed of pilsner malt, light munich and/or vienna. I would lean more towards the latter two b/c from what I remember the taste of Vitus was a bit spicy and bready - slightly sweet upfront with a dry finish. I would avoid using any crystal malts b/c you really want this to be as fermentable as possible while still lending some complexity to the taste.
My first shot at the recipe...
6 Gallon Batch
OG: 1.068
FG: 1.009
ADF: 86%
ABV: 7.88%
SRM: 6.8
IBU: 17
7 lb 5.6 oz Wheat Malt, Pale (2.0 SRM - Wayermann) 50%
4 lb 6.5 oz Light Munich Malt (7.1 SRM - Wayermann) 30%
2 lb 15 oz Vienna Malt (3 SRM - Wayermann) 20%
Mashing: I haven't got a clue yet but it will most likely be a schedule that will focus on high fermentability and creation of compounds to develop banana flavors/aromas - i really need to reread that article.
Edit: Probably just scratch the idea of a step mash and do a 90 minute rest at 145 F and mashout at 165 F. If, after the first attempt, I'm not getting enough banana I will go back and look into a more complex mashing schedule.
Boil: 60 minutes
1 oz Hallertau (4.8% aa) @ 60 minutes - 17 IBU
Yeast: Wyeast 3638, Bavarian Wheat (A Weihenstephan strain). I would probably ferment about 67-68 F - maybe ramp the temperature up slightly near the end to eke out as much attenuation as possible.
After this I would either cold crash in secondary for a month or so, or if I wanted to be more like Weihenstephan I would get a hold of some lager yeast and referment the beer in bottles at a lower temp like 50 F or so and continue to hold that temp for a month or two.