Bob is correct - FBARs are overall very time consuming and confusing and clients do not value that time adequately. Many clients have no idea what foreign accounts they have.
Let's pick on me. I live in London. Pretend I was a US citizen and I was your client for this example. What foreign accounts do I have. Yes I have 2 or 3 banks accounts; that's easy. However, is my Sydney Australia Opal transit Card that is roughly AUD$20 in credit an account? Are my 3 Transport for London Oyster cards (2 of which are over-drawn) foreign accounts? Which of my several UK pension plans are foreign accounts? Are gift cards I was given for Xmas from British supermarkets foreign accounts (all UK supermarkets have banking licenses as they all offer bank accounts)? Which of my British credit cards are foreign accounts (they are all sometimes in credit because I pay the same amount each month to simplify my life)? Is my online Lottery account FBAR reportable? How about my (several years dormant) online gambling accounts that I have forgotten how to log into?
These circumstances are fairly typical...how about my iPhone / Apple Pay in the UK...and every other electronic wallet you can think of...
What is the risk for the preparer if any of these items were missed; just $10,000 for each...could be...