More research as I write...this time it's impostors and stolen identities.
Olivia is about to meet a man who claims to be her--well the male version of her: Oliver Wells.
I didn't put much thought into it when it first came up as a plot element, but as I'm about to write that scene it's sort of important to address. Which means learning more about why someone would pretend to be someone else. So off to Wikipedia where I found some very handy info.
There are quite a few reasons to impersonate someone: money, social standing, fresh start, hiding from the law or gain privileges specific to that person.
He does it for fraudulent reasons, so perhaps it's all a con sort of like Cassie Chadwick: who pretended to be a Andrew Carnegie's illegitimate child and gained access to a lot of big loans [that she never paid back].
Mind you, the Wells family is known for inventing...so unless he can invent--he's gonna have to run someday because people will figure it out. Perhaps he's a mechanic.
He does it for opportunities that would otherwise be unavailable to him [like funding].
No good examples of this that I've found so far, except for a similar situation in the anime Full Metal Alchemist. In the episode, the lead characters, who are brothers, meet another pair of brothers that are impersonating them so that they could be apart of an experiment. The intentions are selfish, but not meant to be slander or as part of a con job.
If he goes this route, he's going to be less of a threat--and less conflict overall. Olivia will also be more reluctant to reveal who he really is.
I think Option 1 is more exciting and allows for more conflict. He might actually be able to fix things and managed to pull it off for a while going the Frank Abagnale way of having other people do it for you. It will also not be as bad if Olivia reveals him, because he was tricking them anyway.