First, on the Dem side, Mr Biden will not appear in person. Rather a deep fake of his head will be put up on a computer screen mounted to the platform, adjusted to place the top of his head at the 6'6" mark. This "Max Headroom" version of Mr Biden will realistically answer any question asked with answers typed in from a small committee in his basement and run through a text-to-voice program. Voice, facial details, and most mannerisms will be perfect, except that no confusion will be permitted. Answers will necessarily be delayed as the committee needs to agree on them and insure that they don't contradict previous answers. The delay will be attributed to electronic transmission times. Odd pronunciations due to text-to-voice shortcomings will be written off as on-line noise.
Mr Trumps side will feature a similar screen, probably 80" wide and with a nice gold frame. This split-screen will be showing a still of Trump on one side and his Twitter feed, which Trump will be using to answer his questions, on the other. To keep things even, both sides will be limited to 3 Twitter length character strings per question. Trumps image will be changed from a smile, to a frown, to a contemptuous sneer, depending on his evaluation of the question or Bidens answer.