As a video editor for over a decade, I almost never use a linear speed curve for an animation. I use easing options and smooth out keyframes to make animations look less rigid. One of my problems with PTE AV is how many times I had to click add modifier > animation speed > then input my settings. The first time I used it, I though just using the Smooth animation speed would be enough but honestly, it's not too different from using the default speed with both its accel. and decel. time (%) set at 26. Funny thing is when I choose Custom, both are set at 50 which feels like the supposed values for a smooth pan, zoom, etc. Maybe someone can vouch for me. Just test out an image panning from one side of the screen to the other for one second at default settings without modifiers vs smooth vs custom. Tell me which of the 3 feels more professional?
So for my suggestion:
1. change default animation speed to have 50 accel. time (%) and 50 decel. time (%).
2. just have linear as an option in the modifiers.