So, I posted my bodice dilemma on the Panniers Livejournal group. There was only one response, but it was very helpful. The type of bodice I've been looking at is simply called the Grand Habit. It's laced up the centre back, no pleating of any sort. Here's a page of pictures and research (in Danish) : Den Franske hof stil (the link at the bottom goes to his reproduction of a Danish court gown, with lots of wonderful pictures)

After a bit more research, I've found these portraits of Queen Marie Leszczyńska, which I think may have served as inspiration for the gown in the anime :



She certainly seemed to like this style of gown, I've only seen one or two portraits where she's wearing something different. Anyway, as you can see in the second portrait, the way the cloak is falling gives a sort of false impression that there's pleating to make a saque back. In almost every portrait, she has a cloak of some sort that she's wearing with the gown, even when it's not the cloak of office. (Notice how there's always a crown in the background, the ermine cloak, and the fleur de lis? Just in case you forgot she was queen. )
So, I've decided that this is the way I'm going to go, the grand habit with the cloak. Maybe I could pin the cloak to the waistline to keep it out of the way and give the same impression as the anime gown? I haven't decided yet, but I'll probably leave it loose.
I look forward to getting started on this. Next step is choosing the fabrics!