Also, it can even be that you cannot rewire your existing brain while keeping all its current functionality and not increasing its size.
But I look at evidence about learning (including learning to see using photoelements stimulating non-visual neurons and learning of new motor skills). Also, it looks like selection by brain size went quite efficiently during human evolution and we want just to shift the equilibrium. I do think that building an upload at all would require good enough understanding of cortex structure that you would be able to increase neuron count and then learn to use the improved brain using the normal learning methods.
Everything you said is true.
Also, it can even be that you cannot rewire your existing brain while keeping all its current functionality and not increasing its size.
But I look at evidence about learning (including learning to see using photoelements stimulating non-visual neurons and learning of new motor skills). Also, it looks like selection by brain size went quite efficiently during human evolution and we want just to shift the equilibrium. I do think that building an upload at all would require good enough understanding of cortex structure that you would be able to increase neuron count and then learn to use the improved brain using the normal learning methods.