If by "backup" you mean something to grab quickly when you break a string onstage midsong, then a stock 7321 should be fine for that. You shouldn't need to change out the pickups or bridge on it. If you really only need a backup for that reason though, I'd get something a little different, that might actually encourage you to slip it into the mix as a guitar for certain other songs. Get something with a
fixed bridge maybe (like a Dean or Schecter), and if you need to dive just find a way to wing it

If by backup you mean something to use as your main guitar all night for a few gigs while your 1527 is in the shop getting setup, then the 7321 likely won't do. Other than that though, I don't see a big problem.
jim