Keep in mind that they already know the outcome of the trial, and everyone on the "jury" already is aware of all the evidence. Team Trump won't actually be launching a defense in any meaningful sense of the word. This is a campaign commercial, on both sides.
My guess is that they will talk as much as possible about Ukranian corruption, the need to investigate it, and they will say the name "Biden" as much as possible.
I would be stunned if Trump's team used anywhere near their allotted 24 hours.
That's all well and good for senators who are in safe seats and not up for re-election in this cycle. The point will not be the outcome, but whether vulnerable GOP senators are willing to advocate for a real trial with witnesses and evidence. My GOP senator is going to be in serious trouble if they don't push back at least a little on McConnell's efforts to bury this thing. The time thing itself might not be too bad. Plenty of it will be in prime time. I think the House managers can fill every bit of 24 hours up painting a picture of a Trump who doesn't give a **** about corruption (and who is now pushing for looser bribery laws), who cared only for an announcement from Ukraine, who only released aid when exposure was imminent, who said the ambassador was going to go through some things (and what things? She'd already been recalled), who trashed-tweeted a witness in real time, who called repeatedly to out a protected whistleblower, who went into cover-up mode way back in July, and it goes on and on. They can point out that GOP House members had equal time to question witnesses and that Trump ordered other witnesses - who would surely would have backed him up, even if they had to lie like rugs - to refuse to testify.
You may think none of that is a big deal but if presented well it's going to be binge-worthy television not just to Trump's detractors but to the whole country and globally as well.
Meanwhile the GOP will do as you say and attack Biden over and over again without being able to show a shred of a real defense.
If commercials they be, they'd best be as entertaining as possible and the House managers have much better material. They actually don't need to grandstand because they have an interesting *story* to tell while Team Trump will be rehashing a 6-page letter that was already a rehash of Trump's feeble tweets and tantrums. It will be boring. I dislike the overuse of the word "narrative" but in this case the House managers have one while the defense is limited to repeating a bunch of weak ejaculations that are for the most part laughably lacking in substance to begin with.
And does his team really want to say that only bribery and treason count? Because there's a strong argument that this was bribery, and his lead lawyer has said actual treason - allowing a foreign adversary to seize and occupy Alaska, thus ceding a large piece of the U.S. to Russia - would not be impeachable. It wouldn't be a crime, either. Then what would it be? Tiddlywinks? I do so hope Dershowitz uses this example in his opening.