Cyclops in middle of room, limited and destructible cover, boss has two main attacks that randomly target certain team members (blasts, laser beams, laser walls that circle room and force movement). Floor can be electrified. Every 20% HP lost, boss is immune until you kill a Praetorian and take an object it drops to opposite side of room to plug it in, more team members carrying makes it go faster, one person is very slow, randomized maze spawns that you must navigate with object.
Some variations for Hard mode and an additional Challenge mode. Hard mode has bonus phase where full body emerges from ground and runs around when you think cyclops is dead. Focus on more mechanical complexity, being cheese proof, etc. Honestly a pretty good idea, as far as hypothetical nonsense goes (even if I like my Crota: A Link to the Past Edition nonsense design better, haha).
He has a 7 min video comparing VoG and CE that gets a lot of stuff right, like understanding you need to do Atheon at Lv29 with 300 Atk weapons to fairly compare it to Scrota at Lv32 with 331 weapons. Although it does get some stuff way wrong, like excusing CE simplicity as "thematic" since Hive are dumb and Vex are smart... Hate that cop out. Scrota can create his own dimension but can't come up with anything more creative to protect himself than "only sword hurts"? Total bs. CE is simple because they ran out of production time and money, end of story.
I liked your Crota: A Link to the Past Edition design better than what you described of Datto's idea too.
I find game design mysterious. Any player can think up an encounter design or a whole game design that sounds cool in practice but actually thinking up something that (1) can be accomplished with a resonable budget and (2) is fun to play to a large majority of players (in PvE groups over the internet) and (3) feels new and exciting is a whole different thing IMO. Seems like there is a lot that you need to know about the particulars of game development before you can really think seriously about it.