Games that drastically change course when things are going great typically crash and burn.

When your game is so popular that you have to stop selling and stop marketing the game, you're obviously doing something right.

Changing the core game so drastically would be fixing what isn't broken and is actually more likely to cause players to leave because the game is no longer what they enjoy and paid for.

If your idea is drastically different from the game you are suggesting it for, it's better to frame it as a suggestion for a sequel or the company's next game to use that suggestion.

Which is what your idea falls into: drastically different from what this game is. This game is doing exceptionally well and changing drastically is more likely to drastically harm the game than help.

Your idea isn't bad in and of itself. It's just not good for FFXIV. Maybe for FF's next MMO this would work well.