So since Bitwig 5.0.7 it's possible to center values of Pan,Crossfade, EQ Gain, basically every bidirectional control. Now it will perfectly center to 0db with Midi CC value 64

Now since my last post i found out how they implemented the steps. Since you're the midi-master, i'm 99% sure you already saw it yourself, but in case not, it might be interesting for you:
Everything is still equally distanced (-1.56% and +1.56%, -3.13% and +3.13%, etc, etc.).
Only in the end, close to the maximum values, there's a difference of 1.5%.
So on the minus values, the last step before the maximum is -98.4%, and on the opposite, there's +96.9 instead.
So the right side (values above 64) has one value-step less, and it's the step close to the maximum which got deleted.
But the maximum values will still be -100% and +100%, so i think, this is solved quite good, and i prefer this over "never being able to hit zero" !
Just wanted to share that tiny discovery with you, in case it's helpful for your own scripts

Best