We mustn't try to include worldwide transactions in the blockchain

Why not? I think that's the ultimate goal (even if a little unrealistic at this point).

Because Bitcoin cannot scale at this size as far as I know. We would end with a blockchain hosted by google Grin

So let's have a robust main chain, and use other technology for smaller amounts (but even for this chain, 1MB is not enough)

When people propose other chains for small transactions, I still have the doubt, what IS a small transaction? Who decides that?