If CC is the only SP we add, I agree that we are not a legit playoff team next year. If we add CC plus two other similar guys, then I think we would have enough to at least fancy ourselves potential contenders. If we've got three guys who can go 160 IP with a 4.00-4.50 ERA plus Bundy and Gausman, I think that is enough SP not (not good SP, but enough) that our offense, bullpen, and defense will have a chance to be good enough to get us back in the playoffs. At least a good enough chance that I'd like to take that chance rather than trade everyone away.
I would, of course, hope that we can build a better rotation than stated above to give us an even better hope in 2018.
So you are ok with a multi-year FA deal for Sabathia (say 4 years) as long we commit other multi-year deals for (2-3) other "quality" FA SP?