@stukapooka I'd be happy with Acorn/Oak being a slightly different version of the Imp/Mech and take the team play away. I do like the team idea, but it doesn't work out that well. Make the Mech like it was in GW2 where it didn't regen health since's it's a machine (although it can be healed), and make Oak able to regen as one difference between them. There's no reason they can't make a 'mech' for both teams while making them different but fun and balanced in their own ways, which is a huge point of the games in the first place!
As for the Cadet, I love her the most out of the new characters, but maybe take away the station idea entirely and replace it with the ability to call down a crater maker attack from a station in orbit like calling in an airstrike or something from other games. Then we'd only have to balance the Acorn/Oak with the Imp/Mech for the transform classes. It would certainly fix some of the ways mechs feel so meh in BfN.
I do give them credit for trying something new with the team classes, and if not for how it slammed into the Imp/Mech and pushed it aside, along with the balance issues they've given us, I do like the concepts. But as you said it's hard to make work and have needed more adjustments than almost any other character in BfN. It may be best to scrap it and move on while keeping the new characters as I love them both. I was ok with the horde characters at first, but I spent coins to max them out just so I could stop playing them. They're just not that fun and feel exactly like the filler they are. Don't bring these back in a new game!
Torchwood is pretty cool, but I love the idea of the Acorn/Oak and am happy with the Giga-Torchwood being a boss without the mini version.
If they really wanted to keep Engineer as he is in BfN, I'd say to replace the speed pad as it's not that useful anyway, separate the ammo replenishment idea from the turret and let us place an ammo crate that can be shot and has limited uses before it runs out and need to be placed again to replace the speed pad, make the turret just shoot and not refill ammo, and change the primary to not be so obnoxious to play against; it's especially bad on that first point in Turning Point. But, I'd rather go back to the GW1 or GW2 engineer or maybe use aspects of several of them. I don't feel that having a drone while the Pirate also does, really hurts anything.
The PvE zones do have the same flow, this may be why Plant Town Center is the best by a wide margin and the rest were still fun, but not as good. I'd like to see reasons to go back, more robust quests, more difference between how they flow, and other new ideas to make them more long lasting to enjoy. I do love looking for the hidden things and the puzzles in BfN.