Re: Efficiency gains
Those people are doing nothing whether in the office or at home.
People need motivation.... recognition, interesting work thanks etc.
People need to work in collaborative teams together so they work together on things, this can be done remotely with sharing desk tops and kit.
People not working is a management issue, if your managers are crap then you will have the issues you highlight, get rid of the useless leaches, from the top through the middle ranks except in the small number of places where there are people seriously delivering.