I don't think Jack is the character to fix the problem most people have with Lena's love interests. I suppose he wouldn't be as abusive as Axel, but I wouldn't really call a relationship with him a particularly healthy one based of his GGGB characterization. Ian being Lena's only male LI that she can have a decent relationship with is, from my understanding, where most everyone takes issue. Perhaps she can "fix" Stan to not be such an incel, but... ehh it still doesn't feel good; at least in my opinion.
Thinking on it, Robert, of all people, could have actually filled this role nicely if some of his dialogue was altered slightly in the beggining of the game. Have Ian fight some throw away rando and remove the creepy stalking vibe when going out to get a drink with him in the first chapter, and then let Lena decide if she is going to fuck him to try and save her job be the trigger that turns him into the stalker / black mailer that people take umbridge with. If Lena makes the opposite choice and accepts that she's losing the job, then her relationship with Robert could have continued on be romantic with a more solid foundation.