i know this will be hard but it would be a great addition to tsw5. Another add could be Thamesport to Croydon.
Quick tip: many threads with little to no detail won't get the attention you want. Also, this won't happen. Its too weak to stand on its own and the current SEHS route will not be expanded (again) to accommodate it.
This suggestion could certainly do with much more detail. However, this and many other missing freight branches could theoretically form a list of Freight Branch Line Mini Packs in a similar vain to the passenger branches I have already created Branch Line Mini Pack threads for. This is the only foreseeable way that I can see to eventually get the multiple missing sections of line across multiple routes as many of the said routes will never be extended to include them otherwise.
If DTG were going to do it, they would have included with V1 or V2 of SEHS, so unlikely they would go back and add it. On it's own, not going to add a LAMPOIL factor to a third iteration of the route, not without also including something like the Sheerness Branch and maybe the classic line into Victoria and Charing Cross from Dartford.