Configurable Viewport and Timeline Grids

I propose that the grids in the blender viewports or timelines have configurable periods and zoom level breakpoints.

Especially for the timeline, being able to set the timing grid so that it draws keylines at integer multiples of the actual framerates instead of some arbitrary constant would be extremely helpful for blocking animation, especially motion graphics without its need to set organic breakdown keys.

Currently the timeline grid has two modes, by frame number or seconds. In frame number mode it it draws keylines at either multiples of 10, 5, 2, or 1 depending on the zoom level, regardless of what the framerate is set at.

For framerates that are multiples of 10 this works out for the most part—when working at 30fps being able to see halves at 15fps would be more useful than thirds too—but when working at 24fps or anything that's not a multiple of 10 the gridlines become useless at the best of times and often a distraction.

For the seconds-based mode this gets even more confusing. The gridline DOES round to seconds at low enough zoom levels. But when zoomed in it starts to get drawn at less than intuitive periods.

A scene set to 60fps starts off at 1 second intervals at this mode, but zoom in close and they snap to multiples of 16, a number that has nothing to do with 60. And even though this number is more useful when working on multiples of 8fps, at 24fps, another common standard, a grid operating on 12 frames would be far more useful than one operating at 16 and skipping every so seconds for no reason. Thankfully, once zoomed in a bit closer the grid switches to 4 frame intervals, but then it gets confusing again if you're working on 30fps; so on and so forth.

Therefore I think being able to configure the grid periods and breakpoints for different zoom levels would be a very beneficial for timeline-based productivity.

Same goes for the viewport, for people working in a more precise modeling standard. I understand CAD is not a common enough use-case for Blender, but creating assets for games is , and these assets often need to be made to a standard grid size for certain kinds of games.

Currently we have no choice but to use a multiple of 10 (and so on under zoom levels) when working with any unit system other than metric. Being able to configure it, or at least set a scalable power-of-two grid would be incredibly useful.