brownymasterWhat are the reasons for allowing those 4 and not any others? Is it mainly to preserve most of the metagame or to keep out annoying stuff/nonstandard play (and thus avoid 30 page discussion threads)?
There are several reasons
Cleaner. Less confusion for new players.
Less trolling of lower teams.
White list approach makes more sense. If it doesn't add anything to the gameplay then why allow it? So people can be fags and troll lower teams with DH and FAN scout?
Everything that is important to the NA metagame is being allow. Everything else is just fluff.