These look like a great solution to your summer dressing dilemma! I'll admit I'm a little envious that you can still wear toppers in summer - I wore my billowy kaftan today because it's already hit 31C & the thought of having to wear real clothes makes me want to cry (but the fact that it's just the *start* of summer makes me want to cry even more)!
Anyway lol, weather rant aside, I wonder whether part of why you like the beige cardigan is the lack of collar, plus the ability to add waist definition (with the middle button) without a stiffly structured waist? If so, it might help to look for some collarless shackets too?
PS - I think Angie has some videos or past posts explaining how to scrunch sleeves to get them to stay up. I vaguely remember that using both a roll *&* scrunch technique will effectively tuck sleeves into place?