I'd prefer that McConnell take no action other than to announce he's taking no action until the Article of Impeachment are sent over. I think it's a bad look for Dems, and the longer it drags out, the worse it will look for them.
Also, lets say he does decide to hold a vote anyway and acquit. Pelosi would then send over the Articles with another bit or two of additional information, and demand a trial now that the Senate has the Articles. That'd put the ball back in McConnell's court. He won't want to have a trial, but then he'll get badgered for not holding one.
I'd just let Pelosi's threat twist in the wind. If she does nothing by the end of next year, then hold a vote to acquit after the election so the historical record is closed.