Well, subroutine calling should be a lot cheaper in perl 6, so there ought not be much difference between starting a new block and starting a subroutine. (That's the plan, at least. Whether we can pull it off is another question entirely)
As for #3.... the AST that the parser builds up will be accessible in some fashion, so the sort of macro transformation you have in mind could work on that, basically working on your parsed code as a series of symbols rather than as a series of characters, which'd make the transformation conceptually simpler.
