Your equipment_vehicle.lua is basically not working at all.
"if mods["Krastorio"] then"
should be
"if mods["Krastorio2"] then"
and even changing that gets the equipment_categories not to work. From what i have seen some of your vehicles (pz4)suffer from the same mistake there.
This is working:

data:extend{
{ -- MausTank
type = 'equipment-category',
name = 'kj_maustank'
},
{ -- MausTank
type = 'equipment-grid',
name = 'kj_maustank-grid',
width = 8,
height = 8,
equipment_categories = { 'armor' },
}
}
if mods["Krastorio2"] then

data:extend{
{ -- MausTank
type = 'equipment-category',
name = 'kj_maustank'
},
{ -- MausTank
type = 'equipment-grid',
name = 'kj_maustank-grid',
width = 8,
height = 8,
equipment_categories = { 'armor', 'universal-equipment', 'vtk-armor-plating' },
}
}
end

and in your prototypes - entity - maustank.lua
you need to declare the grid e.g at the bottom
equipment_grid = "kj_maustank-grid",

with that its working fine with K2.

Else nice work with the models a King Tiger and/or Ace Tiger would be nice ;o

Your research in all honours, but the code is supposed to do exactly what it does. To give support for Krastorio(1), which I played with when I made this mod years ago. It's for people who use a privately modified version of the old Krastorio and want this mod to support that.

If you want my vehicles to support Krastorio2 and Bob's Vehicle Equipment however, you should use the compatibility mod I made for that (https://mods.factorio.com/mod/kj_kras_compat).

i used the compat mod, thats why its strange.

What do you mean?