mpw concept is to generate unique (per site) passwords on the fly based on your master password. It also provides a "counter" option to generate a different password for the same site when counter is bumped.
e.g. $ mpw foo.bar -> abc
$ MP_SITECOUNTER=2 mpw foo.bar -> def
This means I need a middle-step (where to bump the env variable) between get_password and gen_password. Is this reasonable? If so, I'll file a PR. Tnx