Secondly, the modules support should be configured so that muddleftpd passes a structure of pointers to common functions (like safe_snprintf, config functions, ect) to the module when it is loaded.

Then, the modules use those pointers to access functions within muddleftpd.

Pros:
1) Can get rid of the -rdynamic switch on gcc, that bloats muddleftpd's executable.
2) Can strip the muddleftpd executable, without killing module functionality.
3) This all means muddleftpd is even more portable.
4) We get to specify only the interface we want modules to access.

Cons:
1) Slower. Function pointers are slower than dynamic linking.
2) More complex.

Admin should be able to specify external modules to load into running muddleftpd. These modules then can add extra commands/functionality, probably based on directory user is in.