It is possible to use VSync in a windowed game, so this is rather on the way JJ2 is written than any technical hurdles. And widescreen resolution could be used in borderless as well, though as I've said, the scaling algorithm in windowed JJ2 would need to be changed to respect the aspect ratio of the selected in-game resolution instead of scaling it all the way, no matter if it's widescreen or 4:3.
How hard it would be to do, I do not know. But it certainly would be possible and should definitely be done at some point in future as less and less graphic cards support old resolutions that are less than 800x600 or even 1024x768. And not everyone wants to play in a small window.
Remember, there are no impossible things, there is only lack of skills needed to complete the task. And I just know JJ2+ team has all what it takes to do this.
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