For the time being, a lot of merits & flaws are going to be taken at a case-by-case basis. Do they make sense to the character based on the history and the rest of the sheet? Are they there to enhance roleplay or is it just stacking dice pools. Did the player take the time to copy down the description and dice rule and add it to the sheet? These are the kinds of things that make a difference between a "yes" and a "no".
There are a mind-boggling number of merits & flaws in all the different books. If something isn't written up be very system or character type specific, then it can probably be taken if makes sense for the character, and you take the time to type the description and notes into the notes second of your sheet so you (and everyone else) remember the details. Please include what book and page it comes from it ifs an obscure merit/flaw.