That should be fine, but I would add another NIC so that you can keep the cameras off the internet - plug all the cameras via a switch into one NIC and then the internet into the other NIC
Hmm that might be a problem - the room where the PoE switch plugs into all of the cameras is different to the room where the BI system will be.
You don't have to build a system thought, most of us simply purchase a refurb off of ebay or amazon. A fraction of the cost you will spend to build. And a 4th, 5th, or 6th generation would be more than sufficient.
Not sure if you've seen the rest of the thread, but that's a difficult option because my dad has very specific size constraints - it's a whole thing. At least this way will satisfy that criteria and also build something that will last him for another decade.
	
 Many of us have the SFF Optiplexes or Hp Pro desk or Elitedesk....Can't speak for the whole forum though....
