I think their immediate aim is to stop any last-minute pardons and executive orders.
Bingo. That is the push for the 25th amendment as well. Trump should, this very minute, pardon himself and everybody else he wants. Even though Trump can fight the 25th... the time Congress can drag it out will be past the 21st.
The best pushback at present might be for states with pro-Trump majority populations to create a coalition of resistance to this illegal government about to be installed in DC, and declare themselves to be in opposition to it, choose a provisional capital and invite Trump to serve as acting president of the coalition. I wouldn’t call it secession, frame it as recognition of the self-exclusion of pro-Marxist “zones of insanity” or whatever one might wish to call places like the west coast and the urban northeast, Chicago and other large Midwest cities.
If the tax revenue stopped flowing to finance all this madness, then it might die off. Better to save the healthy half of the nation than nothing at all.