How significant is the current Hounslow to Chertsey flow? I guess it would be maintained in same way any current Hounslow to Windsor flow is currently maintained - ie with a change of trains.
While direct services between Weybridge and Hounslow have been in place since 2003, first by diversion of off-peak trains to Reading then by the conversion of these trains to stopping services they haven't always existed.
I think the poor connections at Weybridge put many people off going via that way.
It is normal to have a 4 minute connection between an arrival via Chertsey and the Basingstoke stopper, which isn't shown in journey planners as the minimum connection time is 5 minutes. Therefore journey planners show a 20 minute wait for the Woking 455 stopper.
In the other direction, the Basingstoke stopper narrowly misses the service via Chertsey, so you have to use the 455 stopper with a 20 minute connection (at least you can sit on the Chertsey unit). As things stand, the triangle for Chertsey can't depart later as the incoming train is waiting outside.
It is often faster (or at least as fast) to go via Clapham Junction for stations west of Weybridge. A few flows like Hounslow to Guildford do have slightly cheaper "via Virginia Water" tickets (in addition to the usual "Not via London" and "Any Permitted"), but I'd be shocked if more than a very handful of people choose to go that way as the price difference is very little.