I'm late to this one, but I'll chime in agreeing with the consensus that it's not okay. I've been in two situations where soft-playing (different husband/wife couple for each case) clearly checking it down when it's heads-up in big pots. I don't care if they are the SB and BB and no one else put money in. And forget it if someone gets squeezed out of a pot by those two and it gets checked down. Nope. I don't care how "it's okay..." the rest of the room is with it, if you have any new or newish players there that you want to keep, all it takes is the *appearance* of impropriety to plant a seed of doubt and hurt the health of the game.
In the first case this came up for me it was a game I co-ran and we never invited them back. One of our new players saw the hand go down, it was like a set vs flush draw type of hand checked down after the flop. He said "where's the rest of your pot?" And he was right to ask. That guy has been one of my best poker friends for 15 years now. How you handle these spots matters.
If you're worried about variance, run it twice or three times. I could *maybe* see a case if there are cards to come and you chop purely on equity (that's like "run it infinity times"), but this gets weird if you end up teaching everyone at the table how to calculate equities when you don't want them to learn that. I can also see if as you say people love side action, to sell a share of your equity to someone not in the pot. Sounds like a rich and fluid gambooooly game is what you're after, and imo making straight up collusion okay is going to taint any other loose action that people are after.
*edit to add I'll draw a line on the "business" if it ends up taking too long. If it's ten seconds of banter and a decision is made fine, if people are pulling out calculators and doing long division that'll be a no.