Oh, there's even a discussion here) We need to think about the wording; none of the options listed above are suitable. Besides assessing the strength of a block, there's another, more important issue: assessing the possibility of developing without breaking the block. This also needs to be addressed.
And the Grail should definitely be allowed; this ban only clutters the rules.
where are you going with this? You haven't decided on the block yet, and now you want new "ambiguities"? It just smells like trolling without offering any alternative interpretations.