There is nothing wrong with Trident without missiles or missiles without warheads.
I mean, do nuclear weapons actually work? In the YS2 we knew it was largely empty with a lot of electrical gubbins and a big dustbin inside, but was there anything in it?
It mattered not a jot as a deterrent provided we believed it did and provided they believed it did.
To say if it did I wouldn't use it, if in power I would keep it but empty was complete madness.