That could be solved.

Okay. How (without similarly affecting other Instances of the same Symbol)?

JET

Yep. Good one.

The Pathfinder Effect (ex: Merge) would need to be applied to the unstroked contents of the Symbol. The Stroke would be added to the Instance via the Appearance Palette.

Still does not accommodate objects with various stroke weights, or Symbols with content having both stroked and unstroked objects. But does work even if the Symbol contents includes open unfilled paths (so long as they also have a stroke of none):

Does not meet the need of the thread subject, and does not obviate the need for the requested feature: A straightforward option to simply disallow scaling of Strokes contained in Symbols and Brushes.

Both Symbols and Brushes have huge applicability to any kind of recurring-object projects. For example, think of any kind of parts assembly drawings (anything from tricycle assembly instructions to Lego kit instructions) using Symbols and Brush libraries of frequently used fasteners, etc. which have to scaleable. A near universal convention in such drawings is the use of two Stroke weights; thick for object edges with "air behind them", and thin for edges without. In such a Library, one Symbol should suffice for a hex nut of any size. One Pattern Brush should suffice for a bolt of any diameter/length. Or, consider a Symbol Library intended for road maps. One Symbol should suffice for an overpass bridge or intersection drawn to any scale, even if the content involves multiple stroke weights. Such potentials are severely hindered by the omission of an option to disallow scaling of stroke weight.

But for other things, this is a useful trick, nonetheless.

JET

For anyone who may not be following the argument for the need for an option to disallow scaling of stroke weights in Symbols and Brushes:

In both the Bolt Pattern Brush and the Nut Symbol, the Thick and Thin stroke weights were applied as Graphic Styles.

When the Appearance of an application of the Pattern Brush is Expanded, the connections to the Graphic Styles are lost. (Actually, they are lost as soon as you store the artwork in a Brush.)

When a Symbol Instance is Released From Symbol, the connection to the Graphic Styles still exist. In fact, editing the Graphic Style with, for example, a different color, will update the Instances. Yet Stroke Weights are nonetheless unavoidably scaled when an Instance is scaled, despite the Scale Strokes and Effects setting being turned off.

JET

Not as obvious as a simple Don't Scale strokes option would be, but Wade's approach is probably the most convincing one.

It's an AI CS 5 technique.

On the contrary; it works in CS3.