MechaPilot
Explorer
That's actually a good idea. I mean, I don't play 4e and I admit I'm not too familiar with it, but I can easy see creating a fighter maneuver that takes the 4e Comeback daily into something like: "Spend a superiority die. Add the result of this die to your damage total, and heal an amount of HP of an equal amount."
Thank you.
The primary differences between the 4e powers and the way that 5e works are targeted defenses, damage dealt, multiple attacks are only included through certain powers, and the resource structure.
If the powers are an entire action, then use of a power would preclude making multiple attacks in a round (though some powers would effectively make up for this by affecting more than one enemy, such as the lvl 3 fighter power Sweeping Blow).
Powers often use multiples of weapon damage as they increase in level. For single target powers, this effectively constitutes spending all of your multiple attacks on one. For multi-target powers this gets a little trickier to consider as assigning your multiple attacks to different targets. Some of the high level multi-target powers could best be considered as a combination of 5e's Action Surge with dividing multiple attacks among all the targets.
Targeted defenses could be handled in a couple different ways. Personally, I would just use an ability score as the DC, so a power that pushes would use the target's Strength score as the DC instead of adding time and rolls with opposed checks. Although, you could always reverse the attacker rolls concept into a saving throw for the target if you wanted to instead.
The resource structure is probably the biggest concern, as this will balance the damage output of the powers. That said, there are plenty of potential models one could use for this; I have at least four different models in mind: combo points (build them up and spend them during battle), expertise points (a martial spell-point type resource), roll-based (roll against a higher AC for a better potential effect), and momentum-based (using a power leaves you off-balance for a round or two, imposing disadvantage).