But it's allowed to run at 475kgs, the LMP's have to run at 900kgs because that's the rules for them, that's almost double.
And therein lies the real issue I think. The LeMans / ALMS people have rules that make certain technologies possible, and other technologies uncompetitive -- all to "prove the point" or "make a good show" or "appeal to manufacturers." Or, if you're politically minded, to further a political agenda. Take your pick I guess. AT least they didn't seem to slant the rules to favor the French manufacturers, which was the case in earlier years I hear.
For instance -- I asked the Indy guys years ago, back when diesels took hold in ALMS, about running a diesel at Indy. Wayyyy too heavy I was told, and they suggested that the heavy weight limits (low limit) was needed to make the diesel at all possible.
This year I picked up a whiff of the idea that the rules were set so that conventional gas engines were not competitive, favoring the hybrids and diesels and such.
So returning to the Delta concept -- yeah, if you make that Delta weight what the P1 and/or P2 cars weigh, it wouldn't stand a chance. Or if you let the P1 and P2 cars run 1000 pounds, they'd spend the money and lighten the thing up and run faster.
All of this wouldn't have mattered in IndyCar, where everyone is running the same car, which was the original target.