F451 - you have to remember whose empty homes they are. The way people talk about it is as if the homes in question belong to "the people", and speak of the landlords as if they are getting in the way of "the people" from doing what they want to do with "their" homes.
The reality is those homes belong to the landlords, and the only legitimate claim one would have over any one of those homes would only be once they have been purchased from the landlords.
How about this as a 'positive' idea - set up a managing agent business, contact the private landlords about the empty homes and offer to provide them with a management & lettings service which would be funded from rental yields. Enhanced services could be offered at a slightly higher fee. Pitch this right and you could use a new income stream as a selling point to the private landlord, and on your part if you have assessed the viability of such a business correctly, you may even make a profit from it whilst supplying additional homes for let. Hell - I might even get into this myself.
The point is - as you kind of realise - there is little value in getting these homes back into use if it is unviable. There could be a number of viable means to get them back into use - which don't involve the threat of cutting the incomes of the landlords concerned.