Instead of extending Jubilee or Central, I'd attempt to extend the Victoria Line from W'stow Central, stopping at Whipps Cross and Leytonstone, then getting through to Stratford by some means, terminating in the V between the diverging arms of the surface junction. Maybe possible by widening the Central Line shelf alongside the A12 to 4 tracks or maybe partially 3 tracks as it wouldn't be appropriate to extend the entire Vic service to Stratford - A proportion, at least half, would turn back at the new Whipps Cross station which might be constructed in a trench in the wooded area east of the hospital so could have space created fairly easily for an extra platform or two. Note this wouldn't be loading ever more passengers onto the central section of the Victoria Line, an objection to any radial extension to the line. Rather the trains would be doing double duty in picking up orbital journeys from Stratford round to Walthamstow and Finsbury Park. Any more central journeys would be quicker via other routes from the areas served. The Jubilee has a similar U-type route; someone travelling between Docklands and London Bridge doesn't add to West End crowding. I briefly thought about, then quickly dismissed interrunning with the Central between Leytonstone and Leyton. Capacity is the main challenge here as this close in, it is still a busy part of the Central line; the branches haven't yet divided. Then there is signalling compatibility. So a separate pair throughout ideally, maybe with a few short single line sections where cost or difficulty of double was utterly out of proportion.
