I dont think it is that hard to visualise which chunks are loaded - you can choose 1 chunk 3x3=9chunks or 5x5=25 chunks loaded Also press F9 and see all the chunks...
In an open field F9 helps, but if there are walls, it is not convenient. Chunks are often in different places, one chunk at a time, not 3x3
It would require a client side mod. I don't think this is really needed because it's chunk based and you always have the option to toggle the chunk borders with F3 + G, F4, F9...