Impart BP-Z3(2001-2005 Miata engine)knowledge on me

I'm seeking some wisdom on the Miata BP-Z3 cylinder head(2001-2005). I have a potential client with a BP-Z3 head that has absorbed some damaged - see highlighted areas

My concern is milling this to get to good metal, but because this is VVT, is there a way to compensate cam timing/setting for the lost material?

Or does this require a weld up... or is this junk??

What say you........??

How much do you have to shave to get to clean metal? This is the equation to find how much degrees retard you have after shaving/decking. 2*arcsin(shave amount/cam gear radius) = degrees retard