Idea Summary
Interactive Reports and Interactive Grids do not allow for a column-width to be set for a column. I tested several variants, and none worked successfully.

Use Case
Here are some common scenarios where a fixed-character width would be very nice.

1. 2-character State codes
2. 3-character ISO Country codes
3. 5-character ZIP codes
4. n-character (depending on format) phone numbers
5. All date fields (varies by selected format)
6. Most number fields (varies by format)

Preferred Solution (Optional)
A field in the attributes where the default width, in characters, could be set. And, the resulting table would accurately reflect it. In some cases, the title of the column would expand the width. This is OK, but just enough to accommodate the title.