Although it would be impractical in this instance, I wouldn't dismiss completely the supression idea in similar properties.
Even if you live in a flat with a conventional layout you could argue that there is a potential that tenants become trapped in their bedroom in the event of fire. Tenants prop or remove doors, and do other things to put themselves at risk of fire and fire spread!
In most flats tenants would not be alerted of a fire occurring until the stand alone detector in their hallway is sounding.
By the time those residents wake up, realise whats going on, throw some clothes on, the hallway may be smoke logged!
In this scenario tenants are advised to await rescue in their bedrooms (by fire brigades) ie; close door, put bedding underneath the door, open window, call the fire service, and await rescue.
So with that in mind is the provision of a supression system going to be any different? Even if the lounge is untenable the fire will be controlled and won't get bigger, the tenants should be able to remain in their bedrooms safely if the lounge is impassable (there is an inner hall between them afterall)
But I accept that the cost and perception of tenants means the provision of suppression systems isn this scenario is probably a non starter.