I haven't tried it. But think you can do this as follows.
This would require a couple of shutdown and startup on the instance.
1. Create a new initSID.ora file using the current spfile.
2. Start your instance using the initSID.ora file
3. Create the new spfile on the new location
4. Now rename the old spfile on the default location to spfileSID.old
Edit the spfile location in the initSID.ora file to point to the
5. Try starting the instance without specifying the any parameters.
I think the system would fetch the spfile from the new location
and start the instance.
Life is a journey, not a destination!