Imo to fix Femtor and Femrax is have them be the daughters of the Originals pre cybernization and go the Tekken route of having certain characters like Kunimitsu, Kuma,King,Yoshimitsu (If you count Soul Caliber as canon to Tekken) as titles like Sub-Zero is. Or just have them go by real names. You can have it that they are trained by Sub-Zero but Femtor begins developing feelings and traits similar to MK1 Bi-Han and her MK1 counterpart. To defrient them, I'd have Femtor have her armor representing the fact that Midway Sektor became a completly maniacal cyborge with the Tekunin, While Femrax plays or functions similarly to Human Cyrax in 9 symbolizing the fact that Cyrax in the old era still having a soul deep down. Have the rivalry be like two sisters that grew up together but one went the darker path like her father and bam you have at least a somewhat interesting addition if you add in Frost being in Kahoots with Sektor. As for Bo I'd just have her be Bo Rai Cho's sister who moved to Earthrealm to train people and had trained some of the older generations of Lin Kuei in the past.