One way would be to make every sprite it's own scene. Then place them all under a 2D node, using the animation player you toggle manually what sprite is active.
It will look like this:
Here is a zip with the project:
The nice thing about doing it like that, is that you can use Godot's "group" system or even just the signal system to check collisions then.
Most fighting games animate the collisions or do cell checks.
What you are doing here, animating collisions like sprites isn't what collision systems are made for, expect some problems.
The Godot Area2D will be the most stable for what you are doing, since it works like a cell lookup.
Try collisions first and if there is bugs try the Area2D.