Monolithic images are very old school, hardly anyone uses that approach any more. Either people use thin images created using AutoDMG, or use the Apple installer converted in to an installer package.
Then after the OS has been installed you run further steps to enrol to an MDM platform, bind to directory services, push settings, push apps, etc.
Adobe Creative Suite can be packaged in a way that is compatible with this although further work would be needed to push settings out as well.
While root is and has always been disabled as default as an explicit login account root privileges have still been available via the sudo command. SIP is designed to add an extra layer of protection against this. Remember you need to protect not only against dumb *** users, but also more intelligent malware.
DeployStudio does have built-in support for having a master image server and replica image servers which would be in individual subnets with automatic syncing between them. So does JAMF Casper Suite.
In theory if you use DEP - Device Enrolment Protocol, a fresh out of the box Mac can be auto-enrolled to an MDM, which then auto binds to directory services and pushes profiles i.e. settings from the MDM to the client. The latest MDM tools including Profile Manager can also push apps and custom settings.
Using either thin imaging, or an installer package for OS X or DEP all require additional extra work to set things up but once done this is then pretty much automatic and repeatable for as many Macs as needed.
We have all had to accept things move on and we all need to move on our selves. Monolithic imaging is the way of the past. I used to use this approach myself.
The two most common choices these days for pushing apps and settings are either Munki or JAMF. You can either use DeployStudio or JAMF with AutoDMG and/or createOSXInstallPkg to do the initial OS X install.
As an example I have used DeployStudio with a thin image created by AutoDMG which is 'only' 8GB, DeployStudio then runs additional steps to enrol to Profile Manager, bind to OpenDirectory, push initial settings, push initial apps, install and connect to Munki. Munki then installs its own initial set of apps including anti-virus with settings, and when we used it I even had a fully automatic push of Acrobat Pro 9 with all updates. Acrobat Pro 9 is a far, far bigger task then you might think, each of 27 updates has to be individually run in the right order - there is no combo update. Newer versions of Adobe software are much easier to mass deploy.
See the following
http://www.deploystudio.com/
https://www.munki.org/munki/
https://github.com/munki/munki/wiki/Munki-And-Adobe-CC
https://helpx.adobe.com/creative-cloud/packager.html
https://www.munki.org/createOSXinstallPkg/
https://github.com/autopkg/autopkg
https://github.com/MagerValp/AutoDMG
https://github.com/MagerValp/CreateUserPkg
https://github.com/rtrouton/First-Boot-Package-Install
https://derflounder.wordpress.com/2014/04/17/first-boot-package-install-revisite d/
Note: Munki was written by Greg Neagle of Walt Disney Animation Studios and is used (obviously) by WDAS for thousands of Macs. Munki has also been used as the basis for Google's own Simian for tens of thousands of Macs.
And not forgetting - https://www.jamfsoftware.com/