Each his own, but there's plenty of consolidation and simplification to be done if you want which might reduce risk of data loss without impacting performance. For example, running your massive iTunes library on a RAID0 array is unnecessarily risky and none of that content can benefit from the added performance RAID0 provides over a single disk.
I'm not sure how big your active working data set is, but if you haven't already, I would put as much as you can onto SSD when working on a project and then performance of the rest is less important and you can get that off RAID0 and onto something more reliable as well.
Anyway, the reason were having this discussion is because you don't think you could adapt your storage solution to fit with the constraints of the new Mac Pro... And I disagree. I have nearly he exact same data storage types and requirements but due to the way I've set it up, the new Mac Pro will not require me to change anything. It's all up to you.
Starting with the iTunes library - drive dies, replace the drive with the spare I bought at the same time I bought the other drives, restore from external raid 5 - mission accomplished.
Scratch drive - drive dies, replace drive with the spare, restore from external raid 5 - see above.
The working set won't fit onto the SSDs - that was the original plan, (1 for OS & apps, 1 for working set) until I really started to dig around into my runtimes - I'm looking at about 3/4 of a Tb, so it isn't really an option.
I can adapt my storage solution to the nMP - it's just that it will cost about $1,800 to do it, by all means, if you can show me a cheaper way, I'm listening. Keep in mind the following:
Boot drive - 311Gb of OS & applications
Scratch drive - 2.5Tb of data
iTunes drive - 3.48Tb
Backup system for all 3 logical drives. And don't forget all of the peripherals while your are at it.