Don't know the size of the cable spool in question but it sounds like a good plan.
For anyone having trouble seeing what this might look like try plugging the key words "wooden cable spool planter" into a Google Image search and prepare to be amazed at some of the things that have been made using the cable spools. Lots of great ideas out there!
I'm sorry but I can't find the post where someone was using a cable spool as a plant stand; still looking...
