Signing Wolf is more about 145 than the fighter herself. If they wanted a decent boxing crossover they could sign Amanda Serrano, who is younger and far more accomplished.
The UFC can't allow Bellator to have the baddest female title that goes with the heaviest class - contested class that is. The thing is Wolf is really a 155 pounder, same as Kayla Harrison. Maybe Dana should just sign Harrison from PFL, declare her the UFC openweight champ - like they did with Ronda - and then put up a million dollar prize for anyone who can beat her. No need to sign anyone to a division, just one off title fights at openweight.
Harrison can fight whoever, Wolf, Anderson or anyone who can escape Bellator - this assumes Nunes has retired - even Gabi if she can pass USADA. It wouldn't cost much, just Harrison's purse and a nominal fee to the challenger, the million dollars (two or three if you like) only gets paid out if Kayla loses - and if that happens you've got a new star anyway.