That kind of short altar rail that you’ve described might work architecturally in some churches, maybe in a broader flatter church. But if the church is built in a more vertical mode, more Gothic, you’d want to have something taller and ornate, maybe of marble as well.
The choice and the expense of such an update I’m sure would vary on many factors, whatever the choice was it has to be adopted to the particular venue both in style and construction. But even the cheapest, shortest altar rail would cost thousands to retrofit into a church .