I am confused by your question. Do you want to know how to build a broadcast TV station, or what camera you need that will be “good enough” for broadcast TV. Today, all modern cameras are HD, and can be either NTSC or PAL standards. If the TV station you work with does not transmit HD signals, the TV station will downconvert the HD video to PAL – OR they may require you to deliver a tape, or data, in the standard def PAL format. The only person that can answer this question is the TV station that you work with. In the US, many stations will accept HD media, and then downconvert it to standard def. Stations that have no HD capability will require a standard def delivery format (like Sony Beta), and it is the responsibility of the client to downconvert in advance.
All cameras are good for chroma keying. The trick to chroma keying is knowing the lighting technique, so that you have a flat green or blue background that will work with the chroma keyer. All good cameras (like Sony P2 and Sony XDCam EX) will work, but no one can tell you how to light a set for chroma keying properly on a web forum. You can have the best camera in the world, and if your set is not lit correctly, you will get terrible chroma keys in post production.
I think you want a simple answer (buy this camera, and you can do everything) – it doesn’t work this way.
Bob Zelin