I have an unmanaged package with some features for Opportunity. It includes classes, triggers and custom objects.
I'd like to extend that features to Quote and Order. Is it possible to make extension packages that won't conflict with the one already installed?
p.s.: I'd like to avoid the need to make especific classes and custom objects for each package.
No. Unmanaged packages can't be the base for another package, and any conflicting fields, objects, classes, triggers, etc that are conflicting will cause the second package to fail to install.