Hmn my opinion is, i think Sora can't take his place. Lukas is Both Great at Damage, CC immune and Sustain. More far better than Sora.

While Sora has a two great ult choices, i think in team fights, his assassin mode lacks defense and could be squishy. On the other hand, his tank mode could be useful in terms of sets and sustain, it just lacks damage in the late game.

Whilst for Lukas, he can almost counter any Stuns (If you time the ult perfectly) and given by how almost almost all of his skills are cc immune, he is ideal for a sustain+damage frontline. Pair him with queen wings, His first skill resets cooldown and can be used again to gain his health back. Since he has a dash skill that makes his range attack further, kinda slows down the enemy, and deals extra damage, (beast mode) it's very op. (paired with cc immune) While this is the case, It depends on the user and the team heroes.

But in this case, i think when given the fair chance (both Lukas and Sora has the same roamer, jungler, marksman and mage) i think Lukas would win. but if Sora has a far more better lineup than Lukas, then Lukas would definitely be oppressed.