Is it possible to hook in after options have been processed in a certain package or class?

Is it possible to hook in after options have been processed in a certain
package or class?

In other words: Is it possible to scan the input stream of a .sty or .cls
file (without using Perl) for \ProcessOptions\relax and nest some given
code afterwords? (The filehook or etoolbox package dont provide such
macros. Or am I missing something?)
And as a Remark: Is it ethically correct to use such a macro to patch a
package or class? (When I thought about it, I came to the conclusion that
it must be alright to do so in a world where \renewcommand does exist. But
please let me know what you think about it.)