I can book a ticket from Kemsley (my local station) to anywhere, but can't pick it up because there is no TVM. You just have to pick it up from another station
In all honesty, this is a turn up and go journey, I'd use oyster for this. We've had many discussions about Tickets on Departure availability at stations. A quick look at Google Maps, if you head over to South Bermondsey which isn't that far away, you can collect tickets there if you wish.
I do not understand the question, nor the logic (or lack of).