I agree with Kent that it's a stupid idea but probably for very different reasons to him...
You can't have organisations taking the employees of another organisation without their permission and using them for their will, it sets a terrible precedent.
I mean does anybody here own and/or operate a business?
What would you do if you worked in an industry where your employees or equipment can just be taken and used by a competitor (and in your busiest period) without compensation and with support of the government? You'd leave that industry that's what you'd do, you'd get out of there as quickly as possible and move on to greener pastures where people can't screw with your business willy nilly. It's called capital flight, it's screwed many a country or industry that has f##ked around with this sort of stuff.
And what happens when another cashed up promoter smells money and wants to play a game in China in April? What legs would the RLIF and the national leagues have to stand on if they turned down his money when he wants to borrow some of the RFL and NRL's players from their employers for a one off? Then we'll have two games where clubs are potentially gutted for games that they'll see no return from, then if that one is successful it'll be three games in a year, four games, five games, etc, etc, then it'll no longer be a one off and it'll continue that way until it hits peak capacity, then none of the promoters will make any money anymore cause they have flooded the market and squeezed it dry and they'll pull out, and the national competitions will have been devalued to nothing by the goings on and we're left chewed up and spit out with nothing to show for it.
And it's all well and good that it's NRL clubs and players that this is happening too, they'll survive, but what happens when 20, 30, 50+ years down the road there's a brand new competition in (e.g.) Spain and the RFL or NRL decide they want to gut that competition for a game in China, Spain vs the Roos to sell the game to China, what then, the precedent has been set, there's no rational way that you could stop it from happening and not only would it be a very, very bad look for the game in that new competitions home for a huge chunk of it's contracted players to just piss off during the season, it could be disastrous for an up and coming comp that is just trying to find it's feet.
I could go on, but instead I'll just finish with the preparation for the game in Denver has taken a very short term view of things, it's basically prepare for the WC in 2025 and don't worry about any of the consequences of anything after or stemming from it, and in this case the issues could have been fixed or avoided so easily with some minor changes to some rules and some preparation.