Yeah that will work. You want to earth the bridge itself and in turn the strings - that whole plate thing with the saddles on it is the bridge. Putting on the brass pickup plate will mean the bridge and strings are not earthed and it will buzz.
This is how it looks on an normal TL kit - note the hole with the exposed wire just under the cavity. There is no problem just hanging it out of the cavity so its squashed between the bridge and body.
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