Yes and you can use your 18th and 19th Men?

I would say Golden Try for the first 10 minutes of extra time. If any points other than a try are scored then they count after the 10 minutes. If no points are scored after 10 minutes have been played then go onto Golden point.

What about some sort of silver point system?

Where once you've scored your point, the other team have 2 minutes or so to get a point of their own.

If they do, you start the whole process again.
If not, you win.

What happens if you had to play them in the game due to injury?

tough

or get your bottle boys on?

Which ever fan shouts loudest gets to come on!

Leave it as it is. It is exciting and it very rarely happens. Great for the neutral.