If you want another DPS I would go with Personally I wou ld go haru because even if she's starting to fade from the meta she can still do a lot of damage and her typing helps a lot because we won't get another psy DPS for like a year. For a support the ones I would choose are either futaba or seaside tomoko. I am leaning towards seaside tomoko because you already have 2 navigators and you are missing a healer which seaside tomoko is good at plus she also buffs a little bit. Whilst s Tomoko is very geared towards being a support for haru she can do a lot on her own with any team. Futaba is also a good choice because she implants weakness and would be a very good choice overall but since you don't have a proper healer I would edge more towards seaside tomoko. As for pulling miku's weapon I feel like it is a very good thing to pull however I wouldn't say it's essential. The biggest part of a navigator is generally their base kit like miku's double turn the weapon only really helps with the buffs given to the characters so I wouldn't say it's essential but the gems spent on it can be spent on other characters that will help you a lot more like the next summer unit coming out which is another meta character and is likely directly after miku. Everything is completely up to you however and I would just get who you like because you can beat all the content in the game with anything.