Need advice as to whether or not I should use Wordpress Multisite or set things up using "Numerous" Single Sites?
I have a large website that I will be setting up. Potentially about 10,000 pages. There will also be up to 150 different and individual departments. This is for a University.
My original thought, was to set up each individual department as a separate and individual stand along Wordpress site, with it's own Wordpress installation. On the other hand, I could set up a Multisite (Network) and have all of the departments set up as sub sites within the "Master Network".
Since I use InfiniteWP to manage updates and upgrades of plugins, Wordpress core updates, themes, etc., I wasn't so worried about having so many individual installations of Wordpress installed on the server.
My concerns are that if everything is installed under "one" master site, ...
1. The backup files and database for the "entire site (including all the sub sites)" will potentially become huge, with all the photos and documents that will be uploaded (for all of the websites) together. So the backup could be in the gigabytes (GB) for everything together. And I'm concerned that if I'm just doing one backup of everything, using Backup Buddy, etc., that this could become problematic. Even if I broke the backup into sections .. that would simply make the restoration process a bit of a nightmare .. if and when something might need to be restored.
2. If I'm using "many" plugins (over time) .. even thought some sites will use a few, and other sites will use a few, and other sites may use many, that .. if a plugin should fail, and cause a problem on the front end "or" the back end, I'm concerned that ALL of the websites may become affected and could go down. So .. if there's a conflict of a plugin .. during an upgrade, etc. I'm concerned that a problem with a plugin could potentially bring down "ALL OF THE WEBSITES" and become a serious issue .. and require a restoration, etc.
3. If the site was hacked .. that all of the sites would be compromised. Since all the sites are running off of one Wordpress installation, all of the sites could be compromised if something got hacked (maybe a plugin or a theme, etc.) that could allow a hacking of other things.
So .. I'm curious if I'm being paranoid or over worried about things that most likely won't happen.
Or .. in a situation of a large site like this, with concerns of potentially going off line and needing to then be restored, etc., would my consideration of installing 150 websites, as individual sites, and using something like InfiniteWP to manage all the updates and upgrades, be a good idea? This way, if a plugin that I might install for one department should have an issue down the road when it might update, etc., .. the only site or sites that would have a problem .. would be those that are using that specific plugin (and/or combination of plugins). But in this scenario, each site would truly be independent (from an operational standpoint) and each site could be backed up easily on an individual basis (and therefore also restored on an individual basis), etc.
I would greatly appreciate thoughts on this and advice on which way I should proceed.
Please also let me know if there are any other options that I haven't considered, that I should be looking at.