To the contrary......you can absolutely open the neck pocket 2mm to match the neck you want. I did it on my OOTS swirl to accept my Prestige7 neck:
Unfortunately, the only USA made necks for Ibanez were on the '91-'96 USRG's. They had the tension-free neck. Every other neck Ibanez has had has been asian. AFAIK
, all the WizII are MIJ or MIK (mostly MIK.....your RGT is MIK). All WizIII's and Premiums are MII.
You do have several options open to you though.
My favorite would be to find a '97-'02 Super Wiz (17-20, 43-56, 430mm) With the SW you can either re-radius the fretboard to 16" and re-fret OR install a new 16" board with the wood species and inlays of your choice. AI guitars sells them on Ebay. You can also order one from Mai Guitars (I think?) or ET guitars........both are highly respected vendors here.
Another option is to pick up a MIK or MIJ WizII and, if your proficient with a palm sander, sand the profile to suit your own preferences. I did this on an '05 MIJ WizII. After re-profiling it and doing some mods on the body I sent it to LonePhantom. I'm sure I can get him here to comment on how he finished the neck and how well it plays now. You can see his blog on the guitar here:
You also have the option of finding a WizIII that will require either of the mods above plus opening the neck pocket on the body.
Last, your original thought of finding a Premium neck will give you a LOT of bonuses. Assuming your not thinking about the RG1xxv neck, The Wiz Premium will have ,by far, the best fretwork from the factory of all these options. You'll also get offset dots, 5-piece construction instead of the 1-3 piece of the previous necks, and a (possibly) matching quilted headstock. The pocket will obviously have to be matched. The only problem I see with this option is actually finding the neck. It may take a long time to find one. So far, the ebay "hacks" aren't parting out the Premiums.
Being that your in the US, I would send Chris @ Mai guitars an email, or PM him here ( Chris2112) about either a custom neck or fretboard. He does phenomenal work, and his prices are MORE than fair. At the very least, you would have a price to compare against finding a Premium or modding a used neck.