What happens if no column width is provided? Does the document still look good?

Yes, it automatically grows based on content and space, tested in Word Online.

Screenshots of demo/25-table-xml-styles.ts below.

Before:

After:

Hm, from what I can tell, in older versions of the standard it was a required element, but in the newer versions it's optional. So this may cause an issue with word 2007 or older -- worth a test there first.

Looking at the ooxml wml.xsd, it looks like it's required; so probably shouldn't remove it.

  <xsd:complexType name="CT_Tbl">
    <xsd:sequence>
      <xsd:group ref="EG_RangeMarkupElements" minOccurs="0" maxOccurs="unbounded"/>
      <xsd:element name="tblPr" type="CT_TblPr"/>
      <xsd:element name="tblGrid" type="CT_TblGrid"/>
      <xsd:group ref="EG_ContentRowContent" minOccurs="0" maxOccurs="unbounded"/>
    </xsd:sequence>
  </xsd:complexType>

Also it says in the accompanying spec,

If the table grid is omitted, then a new grid shall be constructed from the actual contents of the table assuming
that all grid columns have a width of 0.

So the spec says one thing, but the schema says another. Fun. The schema is what's used by tooling though, so should probably stick to that.

As of now, I don't think this is a good approach because in the xsd schema, it appears w:tblGrid is a required element in w:tbl.

@devoidfury Ok, if so, can this be closed?