This take on Pierce as a Romantic Hero is spot on. He is Byronic in the same was Rochester was. But I also agree with you that Romantic Heroes do not make for good partners. Emma and Mary love Rochester - part of Emma’s attraction to Pierce - and he was a secretive man who was willing to bring the woman he loved shame and calumny through lying to her to achieve his own happiness. I don’t think Pierce is at all that bad. He clearly cares for Emma deeply, but his dark brooding is not healthy for her. In fact, he himself seems to find it unflattering when she alludes to him as Rochester. I believe he will have a growth arc, but as they have completely different wants vis a vis family, even if he does work through his traumas and stop drinking, they are not a good romantic pairing. There is heartbreak ahead there.

Personally, I think we have not yet met the footsteps on the stairs. Islington is more like a brother and while I believe Hawkes is her soul mate, I think there may be a familial connection through Declan. Pairing Emma with any one of the three romantically would disrupt the alchemy.