Press the reset button.
I wouldn't be averse to turning back the clock and begin series 5, right from where series 3 left off. An upside to forgetting series 4, is undoing the mistakes made through out the entire season. It could be explained that during the fire that raged in Wentworth, Bea was knocked unconscious and series 4 was a hallucination she was having, whilst in a coma. To introduce this plot change, because people would likely think she is in hospital from being stabbed by Joan. Nurse Rose (not Nurse Hatchet Face) could be tending to Bea when she revives. Nurse Rose tells Bea; "You're a hero" because she saved Doreen's baby in the fire.
Other additions I would make to improve Wentworth, would be Jess Warner is not strangled by Joan Ferguson. Jess does die though from smoke inhalation. This means there is no murder charge implicating Joan Ferguson. Joan remains 'The Governor', Vera is still second-in-command. The Red Right Hand (meaning no Allie) is not imprisoned in Wentworth, although they are incarcerated in Barnhurst. Franky is still an inmate on H Block. Depending on what the actor's decision is, Matthew Fletcher works at Wentworth still. Sonia Stevens and Jake Stewart can be reintroduced later down the line in series 5, with the audience being forewarned about their evil inclinations. Once again I've written this many times, the reemergence of Jodie Spiteri and Sky Pierson to either conclude their storylines, or to extend their story arcs.
I know television purists will hate this idea because they think keeping the continuity of a show is sacrosanct. Usually I agree with this. 'Dallas' is a good example of when a show makes a major error and isn't scared about putting it right, actually doing something radical about the lapse in judgment. Almost 30 years on, it isn't remembered fondly and is ridiculed for appearing ludicrous. I contend the alternative of a 'Dallas' without Bobby, would have been even more unpopular. So the creative team had the guts, to put the clock back one season and it made the subsequent seasons better, for correcting their miscalculation.
A bonus to establishing alternate timelines, is keeping the audience on tenterhooks and never being able to guess where they might go with a storyline next. A lot of people would probably find this suggestion anathema, having spent 3 months watching something that now becomes irrelevant. I think Wentworth's audience that disliked the narrative of series 4 as I do (which is more people than I assumed there were) would forgive the programme one gigantic rewrite, if it could save the future direction of the show.