Problem with both the helicoil and timeserts is you need to drill out the old thread which means you risk excess metal going back into the sump. It's only a drain plug so of the 2, a Helicoil would more than do the job.

If it were me I think I'd just bite the bullet and change the pan, good opportunity to clean it along with the oil pickup and change the seal anyways.

But.... If you really cbf, try cleaning up the old threads with a tap and dye and just throw some thread tape (Or low strength Loctite Thread Sealant) around the bolt.