Chuck;
The Lefever safety is just a trigger block. I believe your idea of a hammer block or transfer bar would be much easier to implement into the design than an interceptor & likely superior as well. A sear block safety has to be carefully thought out & fitted so it does not leave a gun prone to AD upon taking it off-safe, but that should certainly not be insurmountable.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra