Wish list

[BG Davis]

Everyone has their own wish list; here's mine (in approximate priority order)
......
Color and lighting:
Separate luminance controls for dark and light areas.  (Increase/decrease shadows, Increase/decrease highlights  At present (1/16/2018), increasing contrast forces increase in light areas, leading to blown highlights. 
......and/or
Curves or levels for luminance and chrominance.
...............
Rotate by any amount (in degrees) – useful for fixing tilted videos – with inclusion of a grid or horizontal guideline to get the horizon level.
.........
"Pause" button for playing video in the "play filtered" mode.  Although this exists in normal playback, in "play filtered" mode the "Start/Stop" button sends video back to start of clip.   Makes it hard to search for details, etc.
.........
Partialize "change fps" for speedup/slowdown effect in a portion of a clip.
......
Freeze frame function

[Jan Gruuthuse]

>8 >8
Rotate by any amount (in degrees) – useful for fixing tilted videos – with inclusion of a grid or horizontal guideline to get the horizon level
>8 >8

With enabled OpenGL, if present in your OS, in preferences Avidemux: Edit: Preferences: [Display]: GUI Rendering Options: [v] Enable opengl support.
You can find in Filters: OpenGL:  OpenGL Rotate +° or -° (basic)

YouTube rotated sample: Filter OpenGl: OpenGl Rotate

[eumagga0x2a]

"Pause" button for playing video in the "play filtered" mode.  Although this exists in normal playback, in "play filtered" mode the "Start/Stop" button sends video back to start of clip.   Makes it hard to search for details, etc.

Use filter preview in the video filter manager for that.

Implementing stop mode for filtered video in the main window would IMHO require pretty big changes in Avidemux. I agree that this would be nice to have, but don't hold your breath.

Partialize "change fps" for speedup/slowdown effect in a portion of a clip.

Presumably, this would be pointless without synchronized speedup/slowdown of audio, which is not possible without major refactoring.

Freeze frame function

If you mean a filter which duplicates the current frame for a given duration (this would allow to produce a video out of a single image), then this might be in reach, but again don't expect synchronized audio.

[BG Davis]

"this would be pointless without synchronized speedup/slowdown of audio"
Not at all.  Many people (myself included) don't use ambient audio.  Edit the video, then add audio track created elsewhere (usually using Audacity.

[AQUAR]

A half implemented function would just generate negative comment from all except a few that don't care.