I disagree. I just opened a non-sheet metal part and added a Base Flange. After deleting said Base Flange, the Sheet-Metal feature still exists, and that's where all the sheet metal data is stored. Deleting the Sheet-Metal feature will for sure delete the Base Flange, but deleting the Base Flange should leave the Sheet-Metal feature.
With the file locations set up properly, when I choose "Bend Table" in the drop down, the bend table is automatically selected. However, when I check the box for "Use guage table" the guage table is not automatically selected, although it is in the drop down list so I don't have to search for it. This has always been the case for me since we started using them way back when.
Our sheet metal template has the Sheet-Metal feature in it, and nothing else. In that feature, we have the guage table set up, defaulted to 22ga, and the bend table set up as well. Upon starting a new part, all we have to do is edit that feature, and select which guage we want, then go about our business making the part. It's about as simple as it gets, as far as I'm concerned. The only thing we have to "worry" about is changing the material property after changing the guage.
As far as my "dream" of having the material property linked to the guage, it wouldn't be based on thickness, at least not directly. My ideal scenario would be to put another column in the guage table that links to the custom property. That way, when you change the guage in the drop down, it propagates the corresponding cell in the table to the custom property. I don't see how that would be that hard for SW to add, but they have not done it even though I have spoke with someone about it after sending in an ER.
Just for reference, which version of SW are you running?