Hi, Understand your wonderment here, as I was wondering that too when I saw the box.
Been looking through the 'Schutzenpanzer' book here by Ryton Publishing and it shows one or the other, but not both together. I noticed that in the back of the book the line drawings of the interiors of the /7 and /10 are somewhat different, mainly in the very rear, where the /10 held ammo boxes and the /7 has what I assume to be various engineering items.
Now this isn't to say that such a configuration would not have been possible, as there were lots and lots of adhoc field modifications done to these AFVs--I saw a picture one some site here awhile back of a 251 with a field-added coat of Zimmerit on it!--so combining these two types on one vehicle could not be totally ruled out.
Would kind of like to know if anybody else out there has seen such a photo of a vehicle like this myself.
Good luck and take care, Sgirty