Adding more sweater dresses to your wardrobe also sounds like a good idea, as do ponte knit pants and athleisure wear. Maybe tube pencil skirts in a knit material for Spring/Summer? And how about some knit jackets or blazers for ease of movement? Ooh, what do you think of a fab cape or poncho as a topper to throw on over everything from a dress with leggings, blazer with jeans, Sporty Luxe looks to more dressy outfits for work and leisure?
Other casual pants with a nice amount of stretch might work too. Something like the KUT plaid skinny stretch pants perhaps.
I also love the ease and comfort of their 'Diana' stretch corduroy skinnies, plus they are available in such fun colours.
And I know you don't like jeans for walking, but I would like to suggest the NYDJ's 'Clarissa' skinny ankle jeans anyway. I have them in the light blue, they are extremely comfortable (you can't even tell they are "jeans"), stretchy and not constrictive in the tummy area at all (I walked all over Amsterdam and London with them this year).
All three styles of pants work well with sweaters with asymmetrical hemline like the Halogen tunic sweaters (finding some in machine washable fabrics won't be too hard), and they are also fun with (shorter) poncho style pullovers layered over a crewneck or turtleneck T-shirt top.
I hope we'll get to see many photos of you showing us your evolving style!
P.S. How about adding one or a few more upscale backpacks too (sounds like the one you have now is getting an excellent workout;-) I love the Matt & Nat brand for those:
http://mattandnat.com/shop/handbags/backpacks