Others can comment as well but first challenge might convincing a visa officer the fact you have a banking and finance degree already and work experience in finance that taking a course in financial planning would not make much sense given would your degree and experience not already have this element. Also even attending such a course you have to convince the visa officer that it will improve your prospects in your home country, might be hard with your current degree and experience you already have in the finance industry.
As for a one year PGWP generally not considered long enough given assumes will walk straight into a job on completing a course so general recommendation is to go for a 2 year course.
Maybe you need to consider going for a masters