PXE Network using outdated Windows 10 images. How dangerous is it ?

With the following setup, if the Windows 10 Client image (provided via PXE everytime the clients start) is completely outdated (Build 16299), no antivirus software beeing used and all clients having full internet access, using an outdated firefox...

Just in general, how much of a threat could the outdated client computers become for
a.) the Server (either Hypervisor, or para Virtualization, or OS Level Virtualization)
b.) the whole network and its data
if the clients have full internet access with an outdated browser ?

Or in other words:
How important are Windows Updates in such an PXE environment ? And what could be the worst case scenario in such an environment, if ignoring windows updates completely ?

I read about Rembo / mySHN aka. BpBatch.
I read about "attacking Windows PXE environments".
(like, setting up your own server to infect the clients with your image, or intercept the image from the original server)
I read stories about "Windows Update messing with TFTP".


Im aware how careless this might sound in the 1st place, but before I create a test scenario like this, playing around with various 0 Day exploits'n stuff, I prefer a discussion about it, here at MDL.

 

Ok, as far as I understand, after the outdated Windows 10 images have been applied to the clients, these act just like...an outdated client would act in todays internet.

But what kind of dangers exist, for the Server OS inside of a Hypervisor within the same network ?

Im aware all clients will be "clean" (but still outdated) after a reset.

And Im aware there is much more info needed, for example on network hardware.
Like if there are VLANs and Layer 3 Switches, subnets, antivir software etc.