In reply to afx22:
Depending on your scrambing experience & route finding, you might find the Fiacall Ridge ok. When I did it last march, we approached it via Corie an Lochan to the right side, traversing up from here meaning the butress was avoided. Didn't find it too difficult after that, was able to find a route up without ropes, but as you say footwork is key here to avoid stepping on a cornice by mistake.
Think others have already said a few of the others that I could recommend. Good Effort on doing Ben MacDui, that's a lot of walking but worth it in the end
I know you're not asking for it because you probably know already, but I'd recommend checking the SAIS avalance reports and weather conditions before any days venturing into Scotland in Winter.
Have fun
Jim