I'm not suggesting the Riverside Quarter is not isolated and deserving of a bus route; nor that it should not be served by the 424 - but I think it needs to continue serving Sands End too.
When Hammersmith & Fulham Council introduced the C4 bus (the predecessor to the 424) in the late 1980s it was launched at Sainsbury's in Townmead Road - that was the whole point of it: to connect the (then new) Sainsburys Fulham store to the rest of Fulham and give Sands End its own "hoppa bus" route.
In 2000 it was campaigning by me and my then constituents that persuaded TfL to abandon the useless contractor who operated the route and relaunch it as the 424, extended through Putney to the Heath. I'm somewhat less concerned about the switcharoo with the 485 at this end of the route, though it would be nice if the 424 took people closer to Putney High Street than is proposed.
I'm not sure why someone from the Riverside Quarter would want to go to, say Fulham Broadway, than they would to Putney (or Wandsworth town, or Clapham Junction) - so from that perspective too the new route as it stands makes little sense.