whether it grows fast or slow is not very relevant

Actually it is relevant. If the blockchain grows slower or only as fast as the technology, we'd have no scaling issues. My "Idea" of discarding blockchains after storing the net effect of the blockchain into a new blockchain is the best solution IMO. Slowing down of growth and increasing the amount of Tx per second is actually all we need. I remember as a kid, seeing a 4GB pen drive was something huge. Now I can't even find something with such low storage capacity.

Since there are no non-technological limitations to the hierarchy, you could even make year long blocks. If an exchange do 50 million Tx in a year, we could summerize the net effect of that in a single Tx in the new yearly super-block. Make it possible to pick which blockchain level you need to operate on will make things even easier. We can have expensive Tx that only take milliseconds (for exchanges etc.) and use a daily block to send someone a birthday gift or make travel reservation for an ultra cheap cost.

Thanks for the Comment :-)