Is it feasible to walk there from this station via the Decks, Aqua city and Pallette Town?It would be a back and forward, but it is all within reasonable walking distance. A more efficient route would be to start at Daiba Station and then walk Aquacity - Decks - Palette Town - Oedo Onsen.
With no serious stopping just window shopping could this be done in a few hours?
Yes.
After PalletteTown should we take the train from Aomi station to the Telecom Centre for the onsen or is it just a short walk?
It is one station by the Yurikamome or about a 20 minute walk.