White Glint from AC4 is one of the main ACs in this game.
AC4 story is nothing really special. It's just a bunch of missions that get you cash. In the end, you'll have to beat a dangerous mech and protect your homeland (this isn't until the end of the game).
I don't think online play will be "sweet". If you played AC4, you'll know what I mean. Basically, the one who wins matches in multiplayer is the one who invests the most time in his mech not just in parts, but in tuning. And that's really troublesome for people like me who just want to pick up a mech game and kill people. (tuning is nice, but when it is so hardcore like this, it's not great for the majority of the gamer population)
Features like decaling your parts and mech are still there. I saw a custom where someone made an AC look like the Juggernaut from X-Men.
I think now there's Kojima Blades and Grenades. In AC4, there were only 3 Kojima Weapons (integrated weapon arms, back-mounted cannon, rifle).
You can use customs from AC4, but you'll still have to have the parts data/parts in general on the AC4A save to use it.
Arms Forts can be taken out with a few hits from the blade weapons. Disappointing.
I wish AC was less oriented on their hardcore greasemonkeys and made the gameplay easier to pick up. As said before, the tuning option is good, but it's too much tuning that actually makes it less fun (i have spent countless hours on an AC only to get shredded to pieces).
More maps are needed on AC4, so hopefully this has heaps more.
DLC could help, but I personally would
rent this game at best.