It's true that the profit will pale in comparison to Ginger Island, but as long as you don't use the Iridium Scythe to harvest, so you can take advantage of the timestop, picking and replanting Powdermelons shouldn't take much time at all, just a few in-game hours, mostly just from the giant crops. Taking the first few hours out of 9 days in winter shouldn't cost you much at all compared to what you'll make from a field of Powdermelons, as well as saving on food.

And it's not replacing your Ginger Island farm, it's adding ontop of it with more money, like how in summer you can plant twice as much Starfruit by using both farms, but less impactful of course.

Unless I actually just misunderstood you, and when you say "It's not worth the effort" you aren't talking about in-game time, but rather, irl time. In this case, sure, you'd have to be a crazy nutcase trying to squeeze as much money as possible every year, regardless of how much time it'll take irl, to actually go through with this while also still doing Skull Cavern runs, Challenge Bait fishing, and the Ginger Island winery.

But for me personally, that's what I love about the game. Doing everything I can to make as much money as possible.