Two thoughts.

First, it's the shell that's eating the quotes and backslashes. If you change the shell to a program of your own, you can process these characters however you want. Many programs use the SHELL environment variable to select the shell to run, so changing that might help.

Second, in order for arguments to have gotten through the shell, they must have been quoted properly. quotemeta can quote them properly, even if it's not the same way they were originally quoted.