Great idea and then CPS people should start wearing cameras too, like those cops with body cams.
While it seems to be legal to film whatever you want in your own private home, the judge could still dismiss video evidence on grounds of some violation of personality rights or whatever of the CPS personel.
While I think it´s worth a try with them cameras, if only to be disruptive to the process, I wouldn´t get my hopes up too much, since I think the CPS, the law, the judges, they are all on the same side, all part of the same crew.
If you choose to subscribe to the idea, that this whole CPS problem is systemic, then there is also not much help to be expected from the courts.
But sure, those cameras would help to actually film real procedures and behaviour of CPS personel, and if seen by thousands of people on Youtube, Twitter, whatever, it could cause a public outcry and become more disruptive to the process.