Rhino V3, V4, V5 user, here.

Forgive my ignorance, but what do you guys mean by "2.5D"?

I use Rhino for 2D linework for my LASER-Engraver (exported as DXF), and for 3D Jewelry designs (intricate small pieces with bezels, galleries, etc. and in this case, once I'm done with the model, it's exported into STL and either carved into resin on a CNC-Mill, or grown into resin on EnvisionTec, Asiga, or FormLabs 3D-Printers).

Once I know what you guys mean, I can tell you how Rhino would go about creating stuff like that.