I understand that the spot deadzone is easier if the axes are locked, but don't see the requirement.
Also, I think you could get away without any major UI revamp, just a "small" new (experimental) feature added.
I was hoping you would employ me to implement this

, but as I need the feature more than I need the job, I'm just gonna lay out my ideas right here:
(This is difficult to explain using only words, but I will give it a go.)
Create a new kind of control point, one which can be affected by the movement of another axis. For experimental version, lets say that this control point must be closest to the middle control point and yield the same value, usually zero. Let's call these "deadzone control points".
Now imagine the two connected axes on the same graph, perpendicular to each other, crossing at each other's origin, and a spot (deadzone) area around the origins.
This spot might be circular for axes with same scaling, or oval (wider in either way) for the general case. The exact shape is determine by the distance of the deadzone control points from their respective middle points.
Create a function for one axis value at the edge of the spot over the other axis true value.
An axis current deadzone might now be calculated as the (above) function value over the other other axis true value.
This means that when yawing, the pitch deadzone will contract. I.e. its deadzone control points will "move" towards the middle.
After, and if, this works, and the quirks worked out, one could remove some restrictions from the deadzone control points and discover new and fun behavior.