Dallas is still trying to move their pick, no? Luka could ask out as early as sometime this season if they don't start getting some traction.
Hendricks might eventually replace some of what they lost in Dorian Finney-Smith, but it's going to take a few years to find out. Lively might work as a roll-man and lob threat with gravity at the rim, but that also takes advanced feel and timing that he may or may not ever develop. Plus, Lively is going to need about 20 more pounds. Neither player is going to raise the floor of their franchise as rookies.
You know who would be great for Dallas? Brook Lopez. Massive screens, multiple ways to finish inside, spacing to the corners.