There are many issue with FEM, it is slow but with some simplifications i thing it could be real time on modern PC. FEM software are not designed for interactivity like 3D cad software, also the interaction with the material must be done in a mathematical way by defining deformation or effort you apply on the material. It is far to be as easy to use as 3D software. With a FEM software you could deform the material in a realistic way, and go to a final result depending of the path of your physical interactions, but you cannot design directly the final object assuming constraints of the material are respected.
What seems possible is to use your prefered CAD software and design your shape using only surface primitives,
assuming in you mind that it is a perfect sheet at the origin, which obviously requires experience.
Then, create a polygon approximation of the shape (the CAD software is maybe able to do it for you)
Feed the result in some Mathematica code to compute the constraint that would appear by flattening your design back to the original sheet form.
For example, use a color map, to display on the polygon where the tensile effort are the biggest positive (red) and lowest negative (blue)
Then map back the colored polygon to your original shape, by reimporting in the CAD software.
Then use a design heuristic :
- where the tensile force is to big you have to deform the shape to lower it (give locally more surface to the shape by changing the surounding)
- where the tensile force is to small you have to add some wrinkled (remove locally some surface)
This is just an idea, but if you could add this feature in real time superimposed to your software,
you could have a desgin assistant to follow the perfect sheet deformation constraint...
You can also try to use a physics engine created for games, they can approximate clothes or flat material by a chain, and are realistic.