E.g. if there were 2 players left could they agree to call it a draw and split the pot? If so would both or neither have to show their hand to everyone who folded? Or, for that matter, if a few people are playing could they all agree they don't like their cards and just do a re-deal from scratch?
So firstly the case of agreeing to split the pot. In the case of a home/private game, sure go for it. It's your game you can run it how you all want to. I mean it screams of collusion and I would never as a player at that table agree to it. I'd also be cashing out as it's not a team game and as I said it just reeks of collusion/soft play or team play between players. You can make any deal you want as long as the table agrees to it. In a casino forget that as it's technically a breach of rules as a hand needs to be shown to claim a pot or everyone bar one folds. One high stakes private cash game I dealt before they never agreed to just chopping, but I did on a few occasions see them do some equity payouts and leave a certain amount for the pot to finish the run out(granted cards were face-up). It's important to note in that scenario they were all friends, and didn't want to bust each other as they were playing socially as it was their once a month game. It's also much more common to just run multiple boards and chop it based on who wins each run out.
With regards to redrawing the hand, again in a home/private game go for it, but why bother playing? The majority of the time you're playing poker you will not have premium hands. You won't get what you're describing outside of your own private game and any half decent player shouldn't agree to those terms. I feel both questions really do you a disservice in terms of learning and playing poker correctly, and if you do end up playing even in another private game or casino you'll likely struggle.
If you're playing with friends and want to do your own rules sure go for it no one can stop you, but it's not correct playing rules and again you'll basically be crutching yourselves. I'd also say that, especially in a group of friends, if most agree to something you could be essentially guilting someone to agree when they don't actually want to, i.e. it can be very hard for some people to be the only person to say no, and they'll just go along with everyone else. Plus then if one says no you could probably summarise that they have a decent hand, thus everyone folds, totally not fair to that player. On top of that you said if a few people agree, does that mean that if 6 out of the 8 want to change you'll change the cards? Any decisions should be unanimous for everyone. If one says no that's it, don't question it again. To avoid any annoying/difficult circumstances I'd say just play the game correctly like any casino would run a cash game.
TL;DR - Can you in a private game, sure of course your game your rules, should you, probably not.
In a home game you can do whatever you like--but in a casino or other formal/structured environment, allowing the last two players to split the pot without showing would be an open invitation to collusion. Likewise, allowing the players to decide things like misdeals after they've seen cards is not going to be fair to all players. House dealers and floor persons are there specifically to keep the game fair and ensure that it runs smoothly.
Even in a home game, if it is possible, a neutral arbiter should be used. Perhaps someone who's present but not playing, or dealers could deal themselves out.