No it would not. If it blurs THIS much then it's definitely not intended behavior, but a bug ;) So it should be fixed properly at the source of the problem, not just worked around by cluttering UI with pointless knobs :)
You're probably right. Maybe such a thing as a global overide setting for diffuse maps and bump map slots. So test renders work qucker then at the end you can tweak that knob and get a better end result. ;)
Links to bump topics from before I forgot to link to (still can't find BB's I'm afraid):
http://autode.sk/1vqQpor
http://bit.ly/1vqQqZs
No,
texture filtering does not (or at least in theory should not) affect performance. Seriously, quit requesting nonsense buttons. When you have so blurred textures, then it's simply a bug. Corona has already long history of bugs that caused excessive texture blurring, so it would not be surprise if not all of them were fixed yet. In ideal case, user should not even need to care about texture filtering at all. If some smarter filtering scheme would be implemented, that dumb filter mode switcher and blur amount spinner could be completely gone from bitmap.
You won't get any better or worse, faster or slower results when changing filtering. You currently may, in Corona, but that's just an issue, not really a regular behavior. The reason texture filtering is in 3ds Max implemented the way it is, is because it was implemented back in the day, when renderers had really poor antialiasing that could not handle high frequency textures, so they needed to be blurred in distance to prevent noise, moire and flickering.
Corona standalone for example uses filtering scheme that requires no user input whatsoever.
