NBU databases is the easy part - catalog backup and restore will be easiest (same hostname and Appliance version). If you can provide an NFS mount for basic disk STU to perform catalog backup, it will make the process even easier.
Dealing with dedupe and/or Advanced disk on the Appliance is the difficult part.
What are the sizes and are you duplicating or replicating to alternate storage?
This is how I see your options without consulting engagement:
If all data on Appliance disk resides on alternate storage, then you could expire all disk backups and remove the storage from NBU (there are TNs on how to remove MSDP from NBU).
Only take catalog backup when all 5230 disk storage (MSDP and Advanced Disk) has been removed from NBU.
You can then start clean with MSDP on new Appliance after Catalog recovery.
Consulting will be expensive but clean and less disruptive.
Catalog manipulation services can migrate the master server to the new appliance and demote the current appliance to media server.
This way you can continue to use the 5230 (there are a good number of years left for support).
If you want to decommission the 5230, you can then at your leisure start to duplicate images to the 5240 until you get to a point where you can remove the 5230 from the environment.
My guess is that the original post was not answered because all of us understand the complexity of disk storage on Appliances and that it cannot be unplugged and moved to another server.
There is a saying: "Fools rush in where angels fear to tread..."
I remember looking at this post originally and hoped that someone else with more hands-on experience would reply....
Just out of curiosity:
Did the reseller that you are dealing with, not present you with a migration proposal?
