One more complication to Harry and Lara's relationship, though admittedly it's an obvious complication and not insurmountable in the long-run.
At the present time Harry is poison for Lara; or any other WCV, to touch because of his love protection. Lara will want to find a way to get past Harry's protection; and to a certain extent so will Harry, but his more logical side will want to maintain that protection. If nothing else Harry will feel a different kind of sexual frustration than he has known in the past. Harry was a loner and shy to boot, so he didn't get much action. Now Harry's choice will be, remain celibate or become enslaved and eventually die, even though it would be a great time while it lasted. This isn't something Harry hasn't experienced before. Yes, in Cold Days Harry knew that Maeve wanted to either kill him of get her hooks into him, but I don't think Harry ever respected or feared Maeve the way he does Lara.
On a somewhat speculative note, should another member of House Raith brush up against Harry they will get burned and realize that Lara isn't feeding on Harry and doesn't have control of him. This could cause some dangerous complications. Instead of seeing Harry as Lara's tamed property, other members of the White Court would equate Harry to a live grenade in their midst. It could also reflect poorly on Lara's leadership, leading to possible challenges.