Here is what you are missing in your analysis.
The irony is that if the Democrats plan to create electoral chaos with their mail-in ballot scheme to overwhelm the post office and election vote counters, it will only harm the House and not the President or the Senate.
Since the entire House is up for reelection, there will be no House on January 3 to select a Speaker. More likely, the Republican states that do not use mail-in ballots will have ordinary elections and send their Representative to the House; they will not be affected by counting delays. It will be the Democrat states that can't count and certify their elections that will leave vacancies in the House. The Republican majority of those present will choose their Speaker.
In the Senate, only one-third of the seats are up for election. If those same blue states can't certify a Senator, the governor MUST appoint a replacement to fill the vacancy because Article V requires "equal suffrage in the Senate."
As for the President, the 12th amendment says "The person having the greatest Number of votes for President, shall be the President, if such number be a majority of the whole number of Electors appointed." Blue states that cannot certify their Electors will not count towards the 270 to win. If 20 EV Illinois cannot count their votes, then the threshold drops to 260 to win, and so on with the other blue states. This will motivate blue state legislatures to hold special sessions to appoint their Electors directly, so that the President will be selected without issue.
So the Democrats will be giving up the House, but nothing else, if they follow this tactic. Furthermore, once they do get their counts certified and their Representatives sworn in, if they do finally attain a majority the Speaker still controls the agenda and may try to block a new caucus vote. Just because Democrats eventually retake the majority doesn't necessarily give them to power to immediately replace a Republican Speaker.
-PJ
Ya but also we all have seen how grievance politics works. the Democrats in the House will claim that their role has been usurped by Republicans in the red states, Republicans in the House, and Republicans in the Senate all conspiring to defraud minorities of their representation to decide the incoming President. The MSM media will gladly cover the bleating Democrats as well as BLM leaders and other liberal voices. The Democrat cities will burn more. More Antifa will show up in smaller towns in flyover country. Basically, in this scenario, a de facto civil war will start around January 4.
There will be a power struggle in the beltway. Pelosi’s speakership will be extended due to unforseen extraordinary circumstances not covered in the Constitution and caused by Republican racism. The armed forces leaders, having a choice of who to follow, could in theory split as happend in 1861 after Fort Sumter.
etc.