Dude. PLEASE spend at least a year with this system yourself, before even considering deployment. This system has many moving parts.
You will need as many capture cards as there are video input sources. One video input source can be multiplexed to multiple media directors.
I tend to get very angry with people who think they can get exactly the info they need spoon fed to them, before deploying a massive installation, because these people tend to lack the in depth knowledge needed to support a large installation of this software; they tend to come screaming back to the forum when they trip up.
You have been warned.
Actually, it doesn't matter when you start developing. Day 1 or day 3000, you'll still know nothing unless you get into code. I've been 7 years on this project, as a developer, and when I still don't know anything
If someone wants to jump head first into code, don't suggest they don't. Ever!