Mrs. Spunkelcrief, yes. Mother Summer? No.
I've previously thought of Nichelle Nichols for Mrs. Spunkelcrief.
Probably in her 60's by now. She's probably younger than most of the others. But we've only seen her once. We've seen Liberty and Mai a few times with the Souncil, and Spunkelcrief is only seen in Changes, iirc.
Nichols has the look, but Mrs Spunklecrief's defining traits were that she was old and feeble, and comically small. She could look a sitting Mouse in the eye, and only got halfway around Sanya when hugging him. I picture somebody more on the scale of Linda Hunt, whereas Nochols I think could make a great Martha Liberty
For old Luccio, Ive been leaning towards Jane Lynch, but Im concerned that she will never be able to pull off a serious role, in the same way that the Janitor from scrubs cant. I remember when he showed up in Indiana Jones as a serious character (a spook)and everyone in the theater started cracking up at every word. That is the danger of playing a straight-faced comic relief character; regardless of your acting ability, the audience is conditioned to take it as a joke.