So, Luthor's neat phasing trick reads like this:

What I'm wondering is if the "half his speed value" is his unmodified value before carrying a figure, or not.

For example, could Luthor use phasing and, carry a friendly figure, move 6 squares and make a free ranged combat action?

Thanks!

Replace then modify.. replace to half then modify by -2..

It does not say half of his unmodified speed value, so you must figure up his speed value doing replaces, then modifies. Take that final calculation, then halve it.

I don't think this is a replacement value thing. The way I read it, he could carry someone and if he moves half his printed value or less, he can make the attack.

This. It does not say anything about becoming half or the life. He just has to move less than half his speed value.

This is all correct except for the highlighted word.