In theory that may sound good, however practical experience is valuable.
Can you not begin to work as a RPN where you are working as a PSW? You would be at an advantage for knowing the company, work culture, policies ect.
L&D nurses need to think fast on their feet (as for most nurses). Things can go wrong very quickly. You need to gain experience as an RPN first. Skills are transferable - home care will help you gain confidence in in teaching (SO much teaching in maternity!), surgery will help with IV starts, foley's, bleeds...I could go on, any RPN job you have now will help you with your next one, even with time management and leadership skills.
I would to suggest that you really look at why you were let go. The company knew how much experience you had when you were hired. So was it a lack of confidence, inability to make decisions, poor decisions? I don't want to be rude, but it sounds like there was an other reason.
Get any RPN job and focus on becoming the best at that job, upgrade your skills and knowledge that relate to that job. When you feel confident in that job, then start to look at getting in to maternity. Take a maternity related course and apply for related jobs when you feel you are ready. Keep in mind if your working at a hospital all you need is the seniority to apply, the extra courses don't really matter, they may ask you to do some courses once your hired but seniority will rule.