Apart from what Samurai said the main issue I have with carryables is the route / location.
At the moment the carryable is located either near the attacking teams spawn (Camden) or the defending teams spawn (Canary Wharf), and the route is away from or towards the other teams spawn. This leads to meat-grinder / lemming rush tactics at either the delivery point or the collection point, and little chance of recovery for the defending team.
The single biggest thing SD could do to improve the situation is move the collection and delivery points so they’re perpendicular to each teams spawn location.
Imagine this layout :
[A] ++++++++++++++++ [B]
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
[C] ++++++++++++++++ [D]
Attackers spawn at “A”, defenders spawn at “D”. Object is collected from “C” and delivered to “B”.
This makes it harder for defence to camp either the collection or delivery points, as neither are closer to their spawn than the attackers spawn (thereby relieving the meat-grinder) but it also allows defence to intercept the carrier and return the object.