There does not need to be any modifications to the jib to work with a square top. Square top jibs are new and still in development besides they need major modifications to the rig to work.

If people want to play with square top jibs that is what development classes like f16 are for.

As for the the sail on 1781 and few others they are totally within the current class rules.

I do think the advertising on the sails can be beneficial to the class and should certainly be encouraged.