I would have agreed with you that the catcher's situation was acceptable...in early December, but at that time, we didn't know how severe the back problem for Grandal was. The White Sox did. If Grandal just had repeated leg injuries, then a decent rehab and strengthening program might have had some ability to give him a shot at playing a portion of the season. But, trying to rehab a back injury of the sort that he has seems likely to be a different beast. Learning about that made it seem way less likely that the White Sox have a reliable catcher in Grandal this year, and like it or not - Zavala and Perez with "Maybe Grandal can play through a serious back injury" is not better shape than in most teams. It has an outside chance at working, but it relies very heavily on a guy with a serious back problem.
Is there a good option there? I'm not sure, the right option was to not trade away their third under control catcher last trade deadline if they had a catcher whose back had gone out. Unfortunately, that can't be easily undone right now.
Also worth noting, I think some of the ludicrous trade proposals we've seen (Hendriks for two top 50 prospects from the Dodgers or for the #1 prospect in baseball!) have left people wondering why there hasn't been more done. Furthermore, this was fed by one "Rick Hahn" who said that he would have to do work on the trade market and who has since made...0 substantive trades, which suggests that perhaps this "Rick Hahn" misread the market and misunderstood his organization again.