I'm not an AB myself but, being a part of the ADISC community, it happened to me to think several times about how a *B roleplay session works, and I came up with an idea that maybe could be useful to someone - or maybe someone else has already put into practice.
One of the most important facts when taking care of a real baby is the ability of the baby to communicate with his/her caregiver in a quite limited number of ways, since either the baby's vocabulary and grammar are quite poor, or he/she isn't able to speak at all. In an *B play session, who plays the baby role usually fakes baby talk, but he/she cannot avoid to fully understand what the caregiver says. This is where my idea applies.
Let's say you were doing *B play with, as a daddy/mommy, someone who speaks a language you don't know well, or maybe you don't understand at all. This would put you in the exact same position of a real baby with his/her parents trying to teach him/her to speak.
This leads to some consequences that can make *B play more interesting and realistic: first, since the *baby doesn't have a clue about what is being told him/her, the caregiver will have to use gestures and sounds exactly like when communicating with a real baby, but now because of an actual incommunicability and not something fake. This way, the *baby is in an actually inferior position towards his/her caregiver: he/she cannot understand, he/she cannot express him/herself, he/she cannot communicate anything except in the way a real baby does.
Moreover, it could also be the opportunity to start learning a new language in a fun and unique way!
And, of course, for "service communication" outside the roleplay, the *baby or the daddy/mommy could temporarily switch to a language - such as English - they both have a "mature" understanding of.
What do you think? Has anyone already got experiences to share about this?