I'd suggest adding a hotkey that jumps the position of the cursor in the replay timeline to where that position would be shown in the keyframe timeline given the time keyframes.

For example, if you have a 30 minute long recording, and the current speed is 4x, and and there was a time keyframe at 2 minutes where the time index is 30 minutes, and the cursor on the replay timeline is at 15 minutes, using this hotkey would put the keyframe cursor at 1 minute. (Edit: Unlike the sync timeline hotkey which would put the cursor at 3 minutes 45 seconds)

This would allow people to go through the recording at whatever speed they want, and add a keyframe at the time they paused at, or speed their recording up by more than the 8x limit without having to go to an external video editor without having to have a calculator open on the side

https://www.replaymod.com/docs/#replaying-paths-time-sync
Except it uses the previous time keyframe to position your cursor, cause the other way around doesn't really make much sense workflow-wise afaict.
Since RM 2.5.0, you don't even have to press the hotkey, it'll automatically trigger each frame while the replay is being played.
Just put down a time keyframe, play the replay and it's hard to miss that the cursor on the bottom timeline moves accordingly.

This would allow people to go through the recording at whatever speed they want, and add a keyframe at the time they paused at, or speed their recording up by more than the 8x limit without having to go to an external video editor without having to have a calculator open on the side

This is already possible and always has been. Just move your time keyframes closer together. If you've got auto syncing enabled (which it is by default), just take a look at how the bottom cursor behaves when you move the speed slider, and then pause the replay and extrapolate that behavior.

I'm not sure what you mean, if you set a time keyframe at time 0 with time index 0 and a time keyframe at 5s with time index 20m, then playing the camera path does what you expect, going through a 20 minute replay in 5 seconds, but when playing the replay at normal speed, the keyframe cursor moves 1:1 with the replay cursor and glitches out after 5 seconds. Using the time sync hotkey with the replay cursor at 3 seconds moves the keyframe cursor to 3 seconds, ignoring the time keyframe at 5 seconds. All of that is what would be expected given the description of the time sync hotkey, but not what I'm suggesting.

I'm trying to say that if you have a position in the replay timeline where you want to place a keyframe, it would be helpful to have a hotkey that moves the cursor on the keyframe timeline to where the position of the replay cursor occurs on the keyframe timeline so you can put a keyframe there, if that makes sense.