Basically, GT4 through to GT Sport all use a secondary scripting language to control most of the gameās logic. Pretty much everything that isnāt physics or graphics rendering is driven by it. For GT5 and 6, some folks have been able to reverse engineer those scripts enough for us to be able to understand and even write our own scripts (see some of my posts in the GT6 modding thread where I actually made a used car dealer for GT6).
With so much control over the game, in theory thereās nothing stopping from simply rewriting portions of the game/menu logic to save files locally. After all, I already do it for things like storing the current stock of UCD cars in GT6, so thereās nothing to say we canāt simply say āthis is the userās saved game, theyāve completed these events, own these cars, and have this many creditsā, and rewrite parts that rely on the save to rely on this data instead.
So with that in mind, the theory is that once weāre far enough down the line for GTS/7 to have shut down, weāll also be far enough down the line to understand more about their scripts and hopefully be able to write our own. Once you have direct access to a gameās scripting language the sky is pretty much the limit - you can rewrite functionality or add entirely new things as you see fit, and we hope to do the same to make them work offline some day.