Really if you wanted to turn his sabre red, it still makes perfect sence with Obi giving the sabre to Luke, as it is pretty clear it is the same sabre that Anakin has clip to his belt through the entire film. Just introduce the red sabre when Anakin ignites his sabre in front of the younglings. That easily implies that Palpatine gave him a new one, we don't need some impossible and complicated scene to explain this.
Really if you wanted to turn his sabre red, it still makes perfect sence with Obi giving the sabre to Luke, as it is pretty clear it is the same sabre that Anakin has clip to his belt through the entire film. Just introduce the red sabre when Anakin ignites his sabre in front of the younglings. That easily implies that Palpatine gave him a new one, we don't need some impossible and complicated scene to explain this.