Ideally you should evaluate if a person will be good in the new position, where they will be promoted. Don't know if that's always possible, or how easy it is.

Also, maybe if someone is bad at their job, they should be demoted or otherwise moved. It's another way to break the convergence to people unfit to their positions.

Or simply pay them more without a promotion. That's what bonuses are for.

I'm personally of the opinion that promotion and pay rises should be entirely separate discussions and it should be both possible and normal to get one without the other. In fact you should have to work your new position for at least 6 month after a promotion before you can discuss any pay rise.

That's not a good recipe for retention of quality people.

Promotion should not be into a different job.

If you're doing the same job after your promotion it's not really a promotion, it's just a pay rise with extra steps.