Avril Jones, 59, and Edward Cairney, 77, were convicted of murdering vulnerable teen Margaret, whose body has never been found, at the High Court in Glasgow last year.
Margaret was last seen in December 1999, aged 19, but harrowing evidence heard at the trial of her 'carers' revealed she had been bound to a chair and had her hair hacked off.
The bungalow was demolished as it was deemed unfit for human habitation - but now two 'architecturally designed' houses have been nodded through by Inverclyde Council.
The ultra-modern detached homes are geometrically designed with glass balconies.
'Very sad recent history of the site'
Entrepreneur Minaz Rajabali, 57, and business partner Harinder Singh Kohli, 51, based in the West Midlands, bought Seacroft cottage for £120,000 in 2017.
They were given permission to demolish it.
Background papers submitted as part of the application said: "The designs and materials take inspiration from the sea, the woodlands and the semi-rural location to reflect the location of this plot of land.
"It is essential here to emphasise the very sad recent history of this site.
"It has been at the forefront of a murder inquiry and trial and as such has left this beautiful area of land with a melancholy that really needs to be lifted.
"It is in the interests of the area, and of course the nearby neighbours, to bring new life to this land and erase, where possible, the memory of this dreadful event.
"An exciting new modern development will help achieve this.
"It is of course a very beautiful site being as it is on the south bank of the Clyde Estuary and it has in the past been under-developed for a single house.
"Not only this, the old house, and those of the two neighbours did not take any real advantage of the stunning riverside location and exceptional site."
Fraudulent benefits claims
Cairney and Jones also fraudulently claimed nearly £200,000 in benefits by pretending Margaret was still alive.
Both Jones and Cairney were convicted of murder and attempting to defeat the ends of justice, and Jones was also convicted of fraud - although a judge said they both benefited financially.
They were sentenced to life, and told they would serve 14 years behind bars before being eligible to apply for parole.
Cairney continues to protest his innocence and lodged an appeal in July.