Oh no, it appears I’ve missed out on this thread as well 
Krita already has this functionality. Space + RMB and drag in the timeline to zoom.
I believe another important feature would be a toggle in the Timeline Docker which allows the user to change the unit of measure from frames to seconds, or perhaps include it as an overlay once the user zooms out to a certain level within the timeline. This would aid in syncing animation to audio files such as music, and help with timing of shots to more accessible second intervals.
Another small fix would be to change the entering of values in the Animation Docker. Currently you type in a number, press enter and the whole entry is highlighted for some reason. You can’t even click out of the box within the docker to confirm the entry. This forces you to click in either the Timeline, or elsewhere to confirm, making the whole process inefficient. I’ve had many times where I went through this, wrongly typed in a hotkey with the entry still selected, and ended up jamming the animation playback until I fixed the values again. Just having enter, or a click outside the box in the docker to confirm would be awesome.
I appreciate the efforts to update Krita’s animation capabilities, and I’m glad to assist in any way! (Late as I am)