So I figured it out and it kind of happened in an instant of mad science magic so I don't know how to properly document it so I'll write my thoughts down as quickly as possible.
It was honestly dumb luck that I started multiplying and dividing things and I made this new variable called "move_multiplier" which I divided by the equation used to calculate velocity:
velocity = velocity.linear_interpolate(direction * speed, accel * delta * move_multiplier) / 1.0025
The "1.0025" is what I like to call, "the slog constant" or basically how dampened the movement is for the player. If divided by a small number under 1, it will accelerate the player in a way I do not like while they are in motion. If they are in motion though, this constant makes it so that they will start moving and then reach a max and then stop. I decided to add the move_multiplier first as a way to slow the player when they stopped moving as you suggested but then I gave it a less than 1 value and saw that it added what I can only describe as a "slippery factor" where they would glide off of surfaces and then stop. The movement was a bit too tight than I would have liked it to be and there was no momentum so I thought this was a cool addition. The problem was that this was only affective on floors so what I did was make another variable (which I already had for other reasons but decided to repurpose) called IsAirborne. IsAirborne is a boolean that uses is_on_floor as it's indicator. So what I did was this:
(This is in the _physics_process(delta) function by the way)
if IsAirborne == true:
move_multiplier -= delta
move_multiplier = clamp(move_multiplier, .05 ,.8)
if IsAirborne == false:
move_multiplier += delta
move_multiplier = clamp(move_multiplier, .05 ,.8)
Delta basically keeps account the time passed since the condition is met so the more a player is airborne they will experience a clamp (min and max range) that reduces the value move_multiplier (where small values make the movement more slippery) and in reverse, if the player was not airborne, they would experience less slippery, more grounded movement. I like to think about these values as the "grounded range" that controls how tight the movement is, where move_multiplier is made to go toward .05 (very slippery) when airborne and then on the ground will go to .8 (very tight but some slip for general movement consistency).
I probably inadvertently recreated something someone else already did and it broke part of my auto-bhop functionality but I'll plan to see if I can fix it somehow but right now I'm satisfied I concocted this weird but workable movement system.
I'll go more in depth if you want but I already rambled a lot and I frankly don't know how I even figured it out.