It can't be a human practitioner. Magic would set off the traps. It can't be the Fae since they use glamour and couldn't get past the scan. Black vamps are undead and have no blood flow. A White Court vampire could get the pin and turn the accountant. But planning for that in advance would risk exposing the plan by Lara learning of it, prior to it happening.
Also, the time a Whamp needs to really enthrall somebody isn't trivial. Seduce them into sex, only a few moments. But getting them to walk into the bank and betray someone likely to kill them could take longer. Not only Lara might notice -- I'm sure there's magical checkups on the accountant, too (just because such enthrallments are known!), so you have to grab/enthrall/break-into-vault all in quick succession.
A Blampire could do it by making a Fine Thrall rather than a Renfield -- but again: Fine Thralls take time, and I'd expect if he went missing for that long they'd disable his access.
Even a mortal practitioner could do it, via enthralling magic. They don't need to bring their own magic into the vault if they have enthralled the victim. Again, though, it takes time...
Justin had an entire school-day to work on Elaine (and maybe some time afterwards to reinforce it, while Harry was fleeing (but maybe that time was spent summoning HWWB?)), but when Harry came back to fight Justin, the enthrallment began unraveling directly; she was gone before the fight ended. Justin clearly expected to
eventually have two trustworthy thralls, and not to spend hours per day, every day, reinforcing the magic on a daily basis for the rest of his life. Again: these things take time.
I still believe that enthrallment is one potential route for a merc to fulfill this objective. We just haven't seen anyone who can so swiftly and completely enthrall (just like we hadn't seen skinchanger skills like GG before).
But a Blamp or a mortal practitioner who had "next-level skills" with enthrallment could, potentially, fulfill Nic's needs here.