That's a pretty big question mark!
Are you on a limited budget? There are probably a lot of options for you, but accomplishing 3 static streams and one mixed stream is going to require a little more hardware than a laptop if you catch my drift...
Perhaps you can outline more about the scope of your project and what options you have already explored or are considering.

this is so wrong ..
you need to connect the camera receivers into a decklink cards to get the sd/hd signals then you have to stream each signal alone to a cloud computer if you need more bandwidth and views , then you need more than 60GB rams on that computer , or you can combine all those cameras to 1 computer with decklink studio card with vmix installed, then stream to a cloud computer to youtube , you have to use a RTMP server on your base computer on location to stream the rtmp to the cloud computer then to youtube .

but the best solution and low cost
but a XAIO server from http://www.xaio.us

comes with decklink studio and 64 GB rams, you can stream directly from this server on location to you tube, i`m using one of those XAIO server .

best dynamic workstation server at low cost .

we did sort of such a thing in our early days, but we were able to get the video feeds into our studio van so we could split them up and put the inputs in several different machines so 1 could mix (the others weren't streaming but recording but that makes no difference.

if you can get the signal into multiple systems you can do this as well.

M@ik