Other than space, flashbacks and engagement were one of the mechanics that new players I ran BitD for had a harder time understanding, so I pulled them out.
Even experienced players in my home games tend to forget about flashbacks, I just haven't seen it in play that much.
Adding flashbacks shouldn't be too much of a problem, since the stress trackers are the same.
WoB assumes the GM has some familiarity with BitD, and will be able to introduce rules from the main game, adding complexity as they see fit.
Thanks for that insight. I thought there might have been a specific lore reason for this -- for example, you weren't concerned with flashbacks because this is an "origin story" for the Blades, so they don't technically have a past to flashback to. Another lore possibility was this: for heists, the Blades just weren't sufficiently experienced yet to be able to "foresee" their needs on a heist, or they just didn't have the ability yet to accurately "case a joint." When they gain experience, you can now say "hey, you're getting good at this, so let's say that you did case this place and set up some advantageous things...hence the flashback"