There aren't too many crowd-pleasing interim manager options out there, if any, but Guus Hiddink, the man with the highest win percentage of any Chelsea manager (with at least two games managed) ever, would probably come closest to one. The other preferred options, like Pep Guardiola, Carlo Ancelotti, Diego Simeone, etc, are all either unavailable until the summer or unwilling to be just interim appointments.
But Hiddink has only emerged as a serious rumor in the past few hours. Juande Ramos was already in the news before the surprise sacking, and, according to at least one source, his agent was already in London negotiating before Chelsea pulled the rug out from underneath the manager and the majority of the fanbase. It would not be Chelsea's m.o. to fire a manager without a replacement essentially lined up and ready to sign already. If the negotiations with Ramos had already been going on, that would make him the more likely replacement.
Neither Hiddink nor Ramos have won anything in the past 5-7 years, with the former most recently in charge of a disastrous Euro 2016 qualification campaign for the Netherlands and the latter famous for the terrible results he had with Spurs and Real Madrid in 2008-09 (the same season Hiddink won the FA Cup). Both are vastly experienced managers with many triumphs in their long careers (Hiddink mostly with PSV, Ramos mostly with Sevilla), but following Mourinho at this time is not going to be easy for either one.
Our friends at Managing Madrid recently sat down for an interview with Juande Ramos to talk about his failure to overcome the Barcelona juggernaut and about his plans after the sabbatical he'd taken from the Dnipro job. The 61-year-old claimed he was ready to get back into management, to find a "good project and a good place in which to develop all the work to my style", but it wouldn't be the strangest development if his connections with Michael Emenalo (who, based on his latest interview, wields plenty of power at the club) led him to Chelsea instead for the short-term. We did similarly provide a springboard for our last Interim manager to get back into management, after all, and look at him go now!
In any case, it sounds very much like Hiddink vs. Ramos for the next Chelsea manager, and it would not surprise me to see the later win out. Then again, very little would surprise me at this point.