Hi Stu.

Do you offer custom plugs/harnesses?

He doesn't, but I would. However, I would prefer getting an as complete as possible connectors kit from him. That would mean all needed plugs and terminals, including the ISO and tuner connectors.
Note also that I won't start doing those harnesses before July, 22nd.

Are the stock ones removable from the cage?

Yes, they are. And as far as I know, they can be removed quite easy.

I want one with a female RCA video cable where the mic in cable is present (for my S/PDIF stuff).

Would be a nice thing, yes.

cu,
sven