Changing the way I use my EX2 Ultra 12TB - advice please

Something of a newbie here so would welcome some straight-forward advice: I am using a 2x6TB EX2 Ultra with v2 firmware under OS3, with an iMac with 6TB of external data storage. I am a photographer so have a LOAD of images and big files. I am running out of space on my external storage (also 2x6TB used as 6TB files and 6TB TimeMachine) and thinking about recommissioning my under-utilised EX2 Ultra to use for the TimeMachine backups (probably not using RAID as 6TB is not enough). Can I safely reconfigure the EX2 to restore the original settings ie keeping the application software etc but making all 12TB available? Can I simply copy all the ™ backups off my external drive to get kickstarted and then switch the ™ disk to the EX2 (or do I lose all my current ™ backups?), and how would I do that - drag and drop? Note that internet access to the TM backups on the EX2 wouldn’t be needed. Thanks!

No.

Changing the RAID mode requires a full reformat of all drives in the system.

You would need to safe-harbor your data someplace while you do the reformat, then migrate it back on again. If you have that much data, such migration would likely take a very long time.