1 day to restore 1TB sounds a very long time to me. I can backup over network my home computer that has much more storage than that in a matter of hours.
I would look into why is the restore so slow. Maybe you can upload some stats, including RMAN restore script and log, and some details about the physical layout (disk, cpu's, memory)?
It takes 7 hours not a full day then :)
In theory, if you had a single Gb interface you should be able to transfer 1TB in ~3h (lots of assumptions there). Is that the case? How many CPU's you have on that machine?
You have lots of limitations and my understanding of your environment could be a lot better...
That being said and assuming that your restore is slow due to tape speed, can you not copy the standby over (I assume it is in sync with prod) and change the name?