I'm in favour of some vertical separation of the deck blocks, mainly so that the parts of the sheet don't rub against each other, but the topmost block must always be such that all parts of the sheet lead downwards from the sail. I don't see how a tower can be used, if this is the case.
I put the topmost block on a fixed rope span so that no rigid hardware needs to be added, but it is always below the clew of the sail. If an adjustable rope span is fitted, that topmost block can be higher when under full sail, but then the span needs to be shortened when reefs are taken. Something like this, or putting the sheet blocks on a traveller that can be hauled up to windward, are better ways of sheeting a high AR sail than a tower, I think.