Try this, adjust the values as needed, see if you like it:
- In Range A-B is the player typical velocity range
- Out Range A-B is the jump height we modify before the jump based on the velocity
Essentially, the faster we run, the more shallow and thus shorter the jump will be. Stationary vertical jumps remain quite high, though.
There is also another method of jumping by launching the player, perhaps the above is good enough, do tell!