If the Bakerloo does take over the Hayes/Beckenham Junction branch then won't the frequency increase be needed to make up for the fact that there will no longer be direct services to London Bridge/Cannon Street but also it it is a frequent Underground service will it attract more people to use it?
Yeah, a good point actually.
I'm not 100% but most Hayes branch trains seem to be 8 car or 10 car electrostars or networkers. I'd guess about 480 to 600 seats?
Obviously higher capacity than a 7 car tube train - current Bakerloo trains have 252 seats but an all transverse arrangement like the Jubilee has just 234. The NTfL with more door space per side might have even less. So I suppose you might need to double the frequency if you don't want to upset a lot of people, although it depends on how full these trains actually are before Lewisham / St Johns. Never been down there so I have no idea myself!
Anyway, that might require 16tph and you could then reasonably terminate the rest at New Cross Gate and Lewisham I suppose.