Back in the fall of 1973 when Spiro Agnew's vice presidency was crumbling (along with Nixon's presidency), one of Nelson Rockefeller's toadies in the press launched a trial balloon. He pointed out that the rules of the House do not require the House to choose one of its own as Speaker; the House can reach outside. He suggested that the House remove the senile Carl Albert as Speaker and instead choose the highly regarded and highly qualified Gov. Nelson Rockefeller of New York as Speaker. Although Rockefeller was from the other party, his choice as Speaker would create a "government of national unity" in this time of grave crisis.
Once Rockefeller was speaker and Agnew was gone, Congress would refuse to seat Nixon's choice to replace Agnew. Then Congress would impeach, convict and remove Nixon, thus making Rockefeller the new president who would wisely govern us...la-de-do-dah.
Nixon finessed Rockefeller's play by moving the highly liked Gerald Ford into Agnew's slot.
If the Democrats are serious about removing Cheney and Bush, they would reach outside the House and choose Gore as Speaker. By emphasizing the "theft" of the 2000 election and arguing that Gore has been the rightful president all along, they could make an argument for the removal of the current administration. (Expect the MSM to run documentaries exploring what happened in 2000 with a spin toward "theft".)
Following the old Rockefeller scenario, the first step would be to remove Cheney by one means or another. Then Congress would refuse to ratify Bush's choice for VP. Then Bush would be removed, thus giving the presidency to Gore, "who was the rightful winner in 2000".
While it sounds far-fetched now, keep an eye on this. If the Democrats do indeed take the House and if they are in fact serious about impeachment, look for a non-Pelosi as Speaker.