Sadly, no such bezier curve killer exists… But there is another way…
I’m just uncomfortable telling it to you….
You could turn the trajectory into a path.
A ‘trajectory’ in Bryce is a line of motion created with keyframes. It’s a misleading term, because the line of motion you’ve created is actually TWO things: the line of motion, AND a relative speed calculation. As you say, you can attempt to compensate for the automatic easing of a Bryce trajectory by fiddling with the curves in the AML, but if strictly linear velocity is required, you may be taking all that time you were spending tweaking the trajectory handles and dumping it into the AML.
Turning the trajectory into a path is an attempt to ‘strip out’ the speed component completely and just have the line of motion as a line of motion. No easing. At Time=0 (0%), the object is at the beginning of the path. At Time=12s (100%), the object is at the final location. Acceleration (if any) now has nothing to do with any curves or easing biases on the line of motion.
Speed is now in the domain of the AML completely.
However… I’ve found the implementation of paths to have become very dodgy from Bryce 6 onwards. I don’t RECOMMEND this as a solution, but you may get extremely good results from it… after you save several versions as you test it…