I think the idea of a smaller number of squad mates was always a foregone conclusion. As the article points out, ME2 was all about building the "ultimate team" so it had to be a big, diverse group. Of course part of the trouble is the fact that--aside from Liara--every single squad mate to date may already be dead one way or another, which means that none of them can be essential in ME3. That's somewhat mitigated by Ash and Kaiden being interchangeable (in terms of narrative) but the fact remains, only ONE squad mate is guaranteed to be on Shepard's squad.
So I think what we can expect is a similar arrangement to ME1 with a 6-8 strong squad (depending on survivors) that allows you to balance out abilities to suit your needs. So given that we know Liara will be the pure biotic class and that Ash and Kaiden will fill the soldier & hybrid biotic niche (though it looks like they switched Kaiden from sentinel to vanguard) that leaves the engineer and related hybrid classes left to fill. I'll go out on a limb and presume that's where the new character fits in. Either way, there needs to eb a bare minimum of character to allow even my "looser" Shepard who got almost everyone killed should have the bare minimum for an effective squad (seriously, only Jack, Tali, Ash and Liara survived!)
As for the bit about customising the weapons; I could almost swear someone at Bioware read my post because that is exactly what I've been hoping for...well not *exactly* exactly as I also wanted to be able to fiddle with the weapons' colour scheme too. Oh well.