I really enjoyed the boss mechanic like the one by Aenc Thon in the Dohn Mheg dungeon. He is the frog boss that creates a rail in the middle of the room where you have to run across like a trapeze artist to get to him.

I wish more bosses employed similar mechanics. A lot of boss in ff14 is "dodge the AoE on the ground by moving out of it". But this mainly uses the XY axis. How about something that uses the Z axis?

For example:
Like maybe a donut that has a thin ring that expands outwards. As it gets to you you have to jump over it. Bonus points for extreme/savage that make it thicker so you have to use sprint and use a running jump towards it to jump over.

I'm aware FF14's netcode might not be able to handle Z-axis mechanics like this too well since for example in turn 5 of coil, people used a small dip in the arena to avoid divebombs because XIV doesn't handle the Z-axis well...

However, what they can still do is an intermission phase similar to the frog boss where you run across the rail. Something like it expect with jumping, just jumping from platform to platform like any terrain in the game or like when you try to reach lookout vistas. This should be a simple mechanic to implement. For example, boss moves somewhere. The party has to go from point A to point B, in order to do so you have to jump from platform to platform.