The augment crystal approach does work when the effect has relatively narrow utility, but here, I think the utility is not that narrow...either the "hit
incorporeal" or "bypass DR" will apply rather often.
By comparison to making the weapon adamantine...the comparison doesn't work, for the same reason. Making one's weapon adamantine certainly has no disadvantages, but it rarely gives an advantage. The force weapon effects give an advantage any time the DR is bypassed (which also covers *every* case where adamantine helps, as well as many more) OR against an incorporeal. It also makes *every other* material non-competitive, because special materials *only* bypass materials-related DR. Oh, and if we assume the force blade, as a magical effect, can't be sundered, then that eliminates the other occasional minor advantage. (Mithral's weight reduction so rarely is a factor, that I'm discounting it completely.)
If you also give it a static cost increase, you don't limit whatever *else* is gonna be put onto it. I'd rather that this had a significant opportunity cost, by being a +2 or +3 MPB.
That said, if you want to make it a "special material"...I'd suggest adapting the Cold Iron rule, that it's a "+1 MPB" because of the material. Heck, that makes more sense here than it, to me, than it does for cold iron.
By comparison to making the weapon adamantine...the comparison doesn't work, for the same reason. Making one's weapon adamantine certainly has no disadvantages, but it rarely gives an advantage. The force weapon effects give an advantage any time the DR is bypassed (which also covers *every* case where adamantine helps, as well as many more) OR against an incorporeal. It also makes *every other* material non-competitive, because special materials *only* bypass materials-related DR. Oh, and if we assume the force blade, as a magical effect, can't be sundered, then that eliminates the other occasional minor advantage. (Mithral's weight reduction so rarely is a factor, that I'm discounting it completely.)
If you also give it a static cost increase, you don't limit whatever *else* is gonna be put onto it. I'd rather that this had a significant opportunity cost, by being a +2 or +3 MPB.
That said, if you want to make it a "special material"...I'd suggest adapting the Cold Iron rule, that it's a "+1 MPB" because of the material. Heck, that makes more sense here than it, to me, than it does for cold iron.

