I would be hard to keep drill shavings out of there when you drill for the heli coil. and I'm not sure the heli coil would not unscrew or screw in farther on a plug like that where it is repeatedly taken in and out. In my opinion, if you want to fix it right, remove it and put on new.
You have to take the pan off either way, so replace it... IMO. I would do it right. I do not trust heli-coils or over sized drain plugs.
You have to drill the hole out for the heli-coil so you will get lots of shavings in the pan which is a big no no. So you must take the pan off to make sure you get them all out. Heli-coils can spin within the pan since it is aluminum.
If you could get one of these from auto or marine store, it would work for a while until you get it really fixed. The drain plug is 12mm? I think. if it is the 1/2 inch is close enough.
On my old FZ1, we were able to lift it up on a car lift and re-thread the hole at a friend's tire shop. I don't like the sound of a temp fix to get to a shop.