That... actually works really well.
(and how you do a proper villain plot in a story)
I think Voldemort’s Triwizard Tournament plan was actually Plan B.
The whole thing is ridiculously complicated. Barty Crouch Jr. has to impersonate Moody, keep the real Moody imprisoned for almost an entire school year, manipulate the Goblet of Fire, make sure Harry enters the tournament, control Krum during the final task, and eventually get Harry to touch the Triwizard Cup.
But what if they originally had a much simpler plan?
Remember Moody’s first Defence Against the Dark Arts lesson, where he teaches the students the Unforgivable Curses? Harry is the only student who manages to fight off the Imperius Curse, and Moody keeps putting him through his paces until Harry can completely resist it.
Except Moody isn’t actually Moody.
Barty Crouch Jr. is the one casting Imperio on Harry. And he does it four times.
We’re told this is him demonstrating the curse and teaching Harry what to look for. But why would a Death Eater spend his time training students to resist one of the most useful tools he has?
What if he wasn’t teaching Harry at all?
What if he was testing him?
Maybe Crouch Jr. was trying again and again to find a way to make Imperio stick to Harry. If he could break Harry’s resistance, he wouldn’t need the Triwizard Tournament at all.
And that’s important because this lesson happens before Beauxbatons and Durmstrang arrive, before the Goblet is set up, and before Harry’s name is even entered.
So I don’t think the original plan had anything to do with the tournament.
I think Plan A was to control Harry directly.
If Crouch Jr. could keep Harry under the Imperius Curse, Harry could eventually slip out of Hogwarts unnoticed, make his own way to the graveyard, and nobody would even realise he was missing until it was too late.
No complicated tournament. No bewitched Goblet. No manipulating an entire school year.
Just Imperio Harry, get him to the graveyard, Voldemort returns, and Harry never comes back.
The Triwizard Tournament might have been Plan B because Plan A failed four times in that classroom.