Just going to copy and paste my response to
@GoldenYuiitusin, as he asked me the same thing:
Sorry for getting back to you late.
別格 is the key word. My electronic dictionary says "special case/ an exceptional case"
The Japanese definition for the word is:
- 定められている格式に拘束されないこと。特別の取り扱いをすること。「会社で―の扱いを受ける」
Something that is not restrained by an established rule. Special handled. [Receive first class treatment at the company].
http://dictionary.goo.ne.jp/leaf/jn2/199114/m0u/
I have no intention of haphazardly [allowing] other companies characters from joining the battle, but this is an exceptional case.
Class of his own isn't a bad translation, but neither is exceptional.
From my interpretation, it seems that Sakurai just isn't going to allow just
anyone to join the battle from another company. Of course, what that means and what kind of criteria Sakurai has on 3rd party character selection is a topic that we don't have a lot of information on. Appearing on Nintendo's consoles (as
a courtesy), and limited in amount are the only 'rules', and they probably aren't as concrete as you would like to think. Remember that Heihachi was considered for Smash for Wii U/3DS, and he doesn't have a strong association with Nintendo (even less than Snake!).