It's possible to restore/recreate the following cars?
Most of those cars don't exist outside of a logo, so they would have to be created entirely from scratch, which isn't really 'restoring' them any more.
The GT40 'Mark III' is just a typo for the Mark I that's already in the base game.
The early Elise model with the canvas roof was replaced with a remodelled version because it's basically wedge shaped when viewed from above, someone got the perspective totally wrong. The roof texture won't fit on the newer model, and there's no point in adding a whole duplicate Elise just for a broken model that was deliberately replaced for being bad.
The Stratos 'Rally Car' in Arcade is just the normal car with the racing modification and a few power parts fitted, all of which exist in GT mode already. The other Arcade rally cars are independent car models (although with similarly lazy tuning), which is why I ported them to GT mode.
There's also an absolute limit on how much content the game will handle without crashing, and the game is right at it. That's why I've gone for finishing off existing but unfinished unique cars over entirely recreating those that were never created in the first place. The more custom work I have to do, the less it's Polyphony's cut content and more just a mod making new things, at which point I'd rather do something more interesting than a late Ford Escort. I'm also not an artist, so anything I created from scratch would look noticeably worse than the original content.
As for a 'limit adjuster', it's not so simple - it would take some serious reverse-engineering of the game to figure out where the issues were and relocate things to change it, and the knock-on effects would be enormous. Even 'just' increasing the garage size would then require changing the savegame format since there's space for exactly 100 cars in the save, so everything relating to loading or saving would need to change, including things like loading a guest garage in Arcade mode (plus a ton of places where the game makes assumptions about the total size of the garage structure). None of those hacks would work on a Playstation console either, which sort of defeats the point of a bugfix and restoration mod.
However, as the FAQ says, all of the tools are openly available for others to do these things if they want to, they don't need to be made by me as part of GT2+.