See, that is a big difference, but IDW has been about making huge differences and making them work. For example: Thundercracker abandoning the cons and never really being in to killing. Big departure, but we love it and it works. Perceptor has a sniper eye and was a wrecker for a time. Big departure. Megatron is an autobot (no explanation needed). Star Saber (good thing this is my personal thread. there are some people that may want to kill Roberts for him).
IDW is about making new personalities for old characters and making them work and making us love them, and Arcee is one of those that was changed radically. Yes, I can see why it is a disappointing departure from her loving motherly character we all know, but it works for her.