Like weapon mods or the like.

Even a rune or gem system.. ohh wait well something lorewise. So maybe not tunes and gems, lets stick to weapon modifications..

I think you may be a bit biased after suffering a little burn out.

 I personally still love the assassin, but wish she wasn't so squishy as a melee and the adrenaline was fixed. Still, I could see mixing and matching poisons or shocks/stuns with her if they wanted to add some flavor. Maybe a variant to stealth kills or add ranged on the sniping (lets face it a sniper should hit the far side of the screen or at least shoot as far as the mobs), and she would be fine. They need to give her a bit more survivability when they do the balance patch at the end. 

As far as the crusader, well...yes he's potato, but he should  be. He's a walking tank in either ranged or melee, and that is what he is meant to be. Heavy armor, heavy weapons bruiser to take and provide damage. He is the basic of classes (like a warrior in most RPGs)  and that is how he rolls. 

Also it could be cool if she could phase through enemies (or described as push her way between them),  have an active but none-movable dodge on a attack or more health per hit to make her survive in melee.

I still really like the crusader, guilty I only started and have only played as him, I cannot see myself playing at the other, since I like the more bulky and hulking units in 40k, compared to FB where the more agile characters are more interesting imo:)

I hope we soon get a more final build, I know we signed up to test parts, but still interested in Fortresses.