Server-side characters almost certainly won't be implemented at all as it's a feature very few people want. That aside, you're missing the point. Do players have access to their own save file? 1. If no, then players cannot spawn additional materials without being given admin permissions. Stacking is a non issue. 2. If yes, then players can spawn in additional materials or finished items through several means, including just editing in plain text. Limiting stack size does not prevent this. In either scenario limiting stack size is ineffective.