Bowser is around a head taller than Peach (and fittingly Samus) by reference picture. That's... 2'6" by the measurements you gave, a bit over half of the size gap for Ridley.
That still would be around half of any human fighter above Bowser in regards to comparing raw canon size.
But raw size doesn't always matter in Smash.
What is the biggest matter is PROPORTIONS.
Many Metroid fans hate the Roidley design. They want "Classic" Ridley, and it'd be the design that doesn't truly clash with Pyrosphere Ridley.
Fine. Makes sense. That's his more uniform design.
Let's look at those proportions, going off of that design's adaptation in Brawl.
Namely it's the grounds that he has fairly scrawny limbs, VERY thin neck, and elongated tail.
Congrats, this is the argument that's been done to death.
That Project M mod with the Other M design does make a fairly convincing case for how it can work.
But when we go for the more beloved design when trying to be made into a fighter by fan mods....
Some results are not nearly as pretty.
The Other M design was the far more probable one to be converted into a fighter than the Super Metroid onwards one because its bodyshape was more natural and burly.
Has Bowser been scaled? Up down and sideways in both his own games and Smash. But his body is one that can go through it pretty seemlessly.
Ridley is meant to be a living totem of terror. I'd rather see a design that looks better as a fighter while retaining an intimidating look from the Metroid series to be interpreted in Smash... that people don't despite namely due to the game it's from.