What to do with old air/light shaft?
To get the floorspace and some light, I guess you could paint the attic section brilliant white, or mirror-line it (the light-pipe idea without restricting the size to the size of the light-pipes - perhaps using builders aluminum foil) put a "skylight" on it in the upper bathroom ceiling and put floor-load and fire-rated glass panels in the bathroom floors. Save a corner of the shaft-space for ventilation duct if there is not an independent means of ventilation for these bathrooms.

One reason for the decline of laundry chutes (however awesome they are ;^) ) is that they are a fire hazard (or a fire traveling quickly through your house hazard, more accurately) as a big penetration in the floor assemblies - to a fire, it looks like a chimney. 

If keeping it a a chute, I guess you could still get some light and reduce lost socks by making the walls mostly glass.