Based on your great video Brad Paisley's Maz really breaks up early at about 2 on the volume pot similiar to a Liverpool so I can understand why Brad P. would use the Stangray to get his cleans and chime. The Stangray will stay clean right up to 7 or 8 and I am using the 212 blues.
The RxES is a monster of an amp great tone and gain. The Z-wreck would be a great amp to have and you did a fantastic job on that amp with Ken F. magic applied.
I don't know what the difference is between the early Maz and the next generations, I think there is 3, but you would use the same as what has been discussed.
Not sure who is building one of these I know I'm not.
For the chassis that depends on what type of head cabinet you want to use. The ceriatone cabs from Gabkits are for 17 x 8 x 2 chassis and you can get that in any tolex. Or if your going TW style hardwood or Marshall style?