Why does Aerith's face look more Western than the rest of the cast? Because she's Half Ancient, so making her look more exotic than the mostly quasi-Japanese cast is a good bit of symbolism.
At first glance, it might look like Tifa's bust has been reduced. In actuality, the sports bra added to her new design is compressing them, making them look smaller then they actually are. Similar to real life female marital artist. Additionally, if you think about it, this also fits her at a character level: Tifa was usually a bit shy in the original game. Hell, if you choose to climb up the stairs at the Shinra HQ in the original game, she insists that she follow Cloud and Barret midway through because she realizes that she's wearing a miniskirt. The implications, to say the least, must have flustered her.
In some trailers, you can see people fighting alongside AVALANCHE against Shinra, makes sense as alot of Sector 7 probably aren't happy they dropped the city/are going to drop the city on them. Or alternatively are new AVALANCHE recruits due to not liking Shinra.
It also ties in with Compilation materials and the bigger picture a bit better. Before Barret's branch, there was a much larger group of AVALANCHE that tried to hit Shin-Ra where it hurts, and just about everyone in the slums has voiced displeasure for the corporation at one point or another if they're not apathetic. It makes sense that more potential volunteers would be out there in one fashion or another, instead of just five people and the equivalent of a mercenary handling everything, much less the logistics of where Barret and Jessie would get their infiltration data and bomb recipes to begin with. The fact that Midgar now has side-quests might also go a long way towards the group improving public relations with the slum-dwellers.