interesting, I would suggest to just make a consistent jump height for wall jump (and maybe other power ups?) and one that changes for regular jumps.
the only potential down side is that players might find this confusing, at any case the jump needs to feel a little more responsive to player input.
Regardless of your final decision I would like to mention that the way I implanted this before is that there is a minimum amount of time you have to hold the jump button in order for the character to jump.
the benefits for this approach are
1:the jump button isn't overly sensitive (which matters less when you use space bar, but I like to use up arrow\W)
2:more importantly that gives a minimum jump height.
now you would have a maximum jump height and a minimum jump height, and this is useful when designing a precise jump because as a developer you know exactly what size gup equals an easy jump (max - min) and what size gup are harder jumps (max\\min\\max-d (d>min))
I hope this helps, good luck!