Well, it seems the minimum level for a franchise to need it's own symbol is if they get a stage, as if melee (and I believe SSB) is anything to go by, the symbol will appear when the stage is selected. Items and trophies don't need a symbol because there's never an instance where the symbol will show up, so it's a wasted effort, which is why DR Wright uses the smash symbol.
It also seems that items only get a symbol if they can be attributed to a certain franchise that's already repped or appeared (pokeballs from pokemon, Goroh from F-Zero (come on, as if Captain Falcon wasn't going to return)), otherwise they aren't given a specific one, so it seems items don't call for their own personal symbol.
At the very least, AC has a stage now, and it's not entirely out of the question that it's all it's getting. Granted, it's too early to count out the franchise having no playable characters, but with the pc's and Tom Nook, the likeliest reps for the series, appearing on the sidelines, at te moment it seems to point more to them not being playable. Granted it doesn't discount them, Tom Nook could disappear from the stage if he's playable, but currently we don't know if that's the case.
Still, I'm glad AC is at least guaranteed some rep in Brawl, and on a more significant scale than Sim City at least.
