My Plan To Terraform The Moon

When i was younger i was always confused by other planets moons and couldn't understand why our Moon was named for what it was, wasn't that like calling your child 'Human' which is a ridiculous name but then someone explained it was called Luna and that made sense and kept me happy for a while with Lunar Eclipses and the Astronauts landing on the Lunar Surface but then i realised actually, Luna was the Roman name for the moon after their moon goddess.
So the moon is called Moon which is why it's name is capitalised and a moon is the name of a body circling another Planet although they have proper names like Europa, Phobos, Enceladus, Triton and S/2017 J9 which brings me to the idea of us at some future point going to live on our moon, or the Moon to give it it's proper name.
The first problem is The Moon is too small to hold an atmosphere and has no magnetic field so we would need to terraform it to make it habitable so lets make a plan to do just that.
First, the problem of the missing atmosphere which means we will have to increase the mass of the Moon, the ideal size would be a bit bigger than Mars so if we drag Mars and Mercury over and combine it with the Moon then it would be the right size and have the effect of all that relocation and molten rock heat will give us a magnetic field. Bonus!!
The down side is we will have to wait for the new and improved Moon to cool so we would have to go away, twiddle our thumbs for 60 million years or so and then once its cool enough we can start introducing life forms to photosynthesize a nitrogen/oxygen atmosphere and in 175 million years or so
it will be ready and we can move in, stand in our Lunar Gardens and stare out into the night sky although we would have to redraw our sky-maps because Mars and Mercury wouldn't be there anymore, your standing on them.
All seems a bit of a faff to be honest so how about we just agree to stop making such a mess of the Earth and leave Mars and Mercury where they are?