> The fact that an executable needs to explicitly specify the "interpreter", instead of that being something under control of the OS loader, doesn't seem like a good way of doing it;

The OS loader does control the permissions of what can be read and executed. And the user can execute a file. Why would it be better if you had to execute the loader explicitly to run a program? The same security problem would apply if you convinced somebody else to execute your malicious code. Seems like pretty harmless syntactic convenience.

The issue of ldd executing the program I guess is a thing that could be tightened to avoid foot shooting. Lots of unix programs traditionally were happy to give you lots of rope though.