Don't know about world spec in terms of to be raced at world level, but some more universal 'Sport' IC class would be nice at many levels, though if your talking new engines, with new specs etc for it, that will never happen, and if it did because of tooling costs to create whole new engines, forget it being cheap.
Think as simple as a carb restrictor and control pipe though, and you have something that could actually work, controlled things over the years have worked best when made simple, control how much they can suck and blow, and lots of things even out, or at least enough to create a parity people can live with.
Add in that average Joe can buy any number of engines that already exist, fit the required restrictions and race, remove them and he is open class, nice and simple.
I'm not even sure how all this started though now, I was too lazy to go read the article...