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What sort of minigames? GT5 has licence tests, speed test, drift trials, special events already which I would consider "mini-games" compared to the main game - Racing.
Fun, silly things with cars. Not racing. I don't know, PD could use their imagination.
.If this is supposed to be new features, I think this definitely comes under improvements rather than new features.
Yes you could consider it an improvement but the A-Spec mode of GT has been the same since GT1, if they completely went back to scratch and did it in a completely different way I would class it as a 'new' feature, or at least something you could promote as being something new.
They had top gear in 5, it wasn't much but I wouldn't say this is new as such
Being able to challenge live times/events from celebrites would be new. Top Gear in GT5 was very weak.
Is GTA not this?
No, I'm talking constantly ongoing weekly racing tournaments with small prizes for each one, sometimes in-game, sometimes real world. Forza 2 had these IIRC, without the prizes. It would be new for GT.
Anyway those were just ideas I came up with in 2 minutes, there are surely many others if PD say and thought about it.