The Z7 body is assembled out of cast magnesium parts, it's quite sturdy and well capable of withstanding bending and certainly no risk that the Z-mount bending or coming off during normal use, the screws are directly into the casting unlike many DSLR, even the D810 for instance has plastic under the F-mount itself ,,,
The Z6 and 7 castings are not similar to for instance a D5, the Z body is made out of several parts that are put together, so yes less strong than the some of the Pro DSLR.
There will for sure be a lot of plates both for the FTZ and Z7, may I suggest a bit of patience,,,