There are some things from their PC version of Mordheim that just were bad, and didn't add any enjoyment to the game. Here's some of what I hope they don't keep.
-Time you have to sit out training a character if they level up.
-Wyrdstone or similar gathering.
-Hit points like Mordheim. That system will make 40k weapons seem like a joke, where things could happen like one of your Juves getting a direct hit from a bolter failing his armor save, and is still standing while possible in the TT (fail to wound roll), it was highly unlikely.
-The horrible starting position system for missions. Especially the scatter from a fright one Just use a side deployment system and add placement locations in the whole deployment area and let us decide if we want to break off a strike team to the side or not. And let use place characters on the map.
-Their adaptation of Mordheim's leveling system. Having to by replacements from a merc list was annoying, and actually took away imo from the attrition you could face in the TT game. And starting over at 0 in the late game in Mordheim meant really a waste of a warband member who would get one shot by leveled up opponents unless you just sat him back away from combat, which meant leveling them would take forever. The TT of Mordheim and Necromunda, it wasn't the end of the world for a warband or gang member to die and you having to replace him (unless you really had bad luck and had multiples you couldn't afford to replace). Where in their adaptation of Mordheim, it ended up really affecting strategy in tactics and builds. Survival builds and anti-crit builds became common meta.
I'd like to see a more faithful leveling system like Cynanide Studios did for Bloodbowl which is a pretty close true adaptation of the TT. I like that you didn't always get what you wanted, and had to deal with it. And I liked that in the Mordheim and Necromunda TT also.