[TYPO3] Fancy menu structure - how to manage template inheritation?

[Bruno Brödner]

Hi,
I have a "fancy" menu structure like this:

Tree 1:
-root
  -Welcome
  -Projects
    -Project A
      -Picture Gallery A
    -Project B
      -Picture Gallery B
    -Project C
      -Picture Gallery C
    -Project D
      -Picture Gallery D
  - Contact
  - ...

All pages use the root-template, but I want to have something special 
for the picture galleries. Gallery pages should have a different 
stylesheet and I want to hide some BE fields only for the galleries. So 
I have to make an extension template for *every single* gallery page and 
modify *every single* gallery page's TSconfig.

I could be easier if I could have a structure like that:

Tree 2:
-root
  -Welcome
  -Projects
    -Project A
    -Project B
    -Project C
    -Project D
  -Galleries
    -Picture Gallery A  	
    -Picture Gallery B
    -Picture Gallery C
    -Picture Gallery D
  - Contact
  - ...

With this, I only have to make *one single* extension template and 
TSconfig on "Galleries" and it will be inherited to all galleries below. 
But this is *not* the kind of menu tree, I want to see on the front 
end... it's not very user friendly having projects and galleries in 
different sub trees ...

Is there a way to have an internal structure like tree 2 for an easy 
configuration *and* to have the tree shown in the frontend like tree 1?

Does anyone has a suggestions that pushes me in the right direction? I 
could imagine to use TMENU in a special way that connects each gallery 
page to the project page ...

Kind Regards
Bruno