Thank you!
Definitely space limitations- I cleaved very closely to the 24XX template and this put a solid constraint on how much I was going to squeeze in. There's soooo many other great classes, it's really a rich vein! I'm not going to surprise anyone when I say the Inksmith is my favourite... but Bloodwitch is up there, too. Classes as world building device is clearly something that RRD do very well...
...and this is especially evident in Heart! Hadn't even occurred to me to adapt it too... but of course now that seems like a massively fun idea. I'm going to be too busy for a bit to get round to that, though... why don't you give it a go?