I find it really weird to be having a big debate over the current monk build. It's dead as a doornail; even if you're not already using the 2024 version (you should; it's so much better), it'll be live in a few months anyway.
FoB is great with the new build, because you have a slightly higher damage base, you have more di, crucially, it steps up to allowing three extra attacks at level 10, and it comes off the bonus action, meaning that you can always combine it with the dodge action if necessary. Between that and deflect missile becoming deflect attack, monk are very capable tanks, especially against single opponents.
For example, at level 10, my monk's base attacks, unarmed, each hit for an average of 10.5 damage (d8+5+1 for eldritch claw tattoo); going up to 14 if I need to activate the tattoo for a tough fight. With FoB that's a base of 52.5 or 70 damage per round, which is pretty damned respectable. Even in tank mode, using the dodge action, she's still sitting at a base of 31.5 DPR (plus 14 more from deflect attack if she wants to spend di on that).