Mutants and Masterminds 3e stacking powers and equipment

[thereaper]

I had an idea for a fire-themed weapon user, who can pick up any weapon and set it alight. How would I do this?

[Cazero]

Build the whole power as if you could do it with nothing, then add a flaw. Ask your GM if Easily Removable would be appropriate (it might not be).

[Grod_The_Giant]

Damage X, Strength Based on 2 ranks, Quirk: Requires a weapon

[theVoidWatches]

There's a thing called a floating extra, which is basically an extra that can apply to multiple different attacks. You price out the cost of the extra, and add on Variable Descriptor 1 or 2, depending on how many kinds of attacks it can apply to. Doing it this way is distinct from Cazero and Grod's suggestion because it means that the equipment you're using matters - with a floating extra, a Damage 3 sword that's on fire will hit harder than a Damage 1 Dagger, a whip with Reach 2 will still have Reach 2, etc - with their suggestion, the equipment allows the power to be used, but doesn't contribute to the mechanics of the attack.
Of course, it also ends up being 2 pp cheaper their way, so... trade offs.

I usually suggest Secondary Effect as an extra for flame attacks, representing a continuing burn even after the initial hit.

Secondary Effect X (Variable Descriptor 1: Melee Weapons); X+1 pp

This will deal the same damage again the round after the initial hit (assuming you don't hit them again), up to X. The second hit doesn't have to be as strong, but it can't be stronger.

An alternate version of this is to use Concentration instead of Secondary Effect.

Concentration Y (Variable Descriptor 1: Melee Weapons); Y+1 pp

With this extra, once you hit someone once, the flames continue to burn them for as long as you concentrate, and you can use your action to deal the same damage again (up to Y) by having the fire flare up. This will likely feel a little more magical than Secondary Effect, as you have to actively cause the fire to deal damage, rather than the burn being natural - that may be a bonus or a drawback, depending on how you want your character to feel.

You can power up the hits themselves similarly, by adding extra ranks of damage.

Strength-Linked Damage +Z (Variable Descriptor 1: Melee Weapons); Z+1 pp

This will increase the initial damage of any melee weapon you wield by Z (within power-level limits).

Another possibility would be to give the weapons a level or 2 of Reach, representing the fire flaring up farther than the swing of the weapon itself.

Reach 1 (Variable Descriptor 1: Melee Weapons); 2 pp

Again, this applies to any weapon you wield, and increases the range by 5 feet.

You can take as many of these options as you like, and they'll all work with just a single Variable Descriptor as long as they're all one power (if you want them to have be different options for how the flames behave, they should be separate, which means you can have them as different slots in an array). A PL 10 power for setting your weapons aflame might therefore look like this:

Fiery Wrath
Strength-Linked Damage +4 (Secondary Effect 4, Reach 1, Variable Descriptor 1: Melee Weapons); 10 pp
Fire wraps around any weapon you wield, boosting its damage and continuing to burn after a blow. The flames even leap forth to extend the reach of your strikes.
When you wield a melee weapon, you can use this power to wrap it in fire as you attack. The reach of the weapon is increased by 5 feet, and its damage is increased by 4. One turn after you successfully hit a target, the target must save against Damage 4. This secondary damage doesn't stack with further hits if you successfully strike again.

[Cazero]

There's a thing called a floating extra, which is basically an extra that can apply to multiple different attacks.

Problem is, by RAW you can't stack a power with equipment. However, considering how harmless this one bit is, I'm inclined to just ignore RAW on this.

But if you want to stick to RAW and still have variation based on the weapon you're using, you have to use a Reaction Variable power Limited to mimicking extras of the equipment you're using, and that's stupidly expensive for what it does.

[theVoidWatches]

I believe the rule there is only a general guideline, not a firm rule, because the floating extras in Power Profiles go against it. Or, perhaps, that rule would prevent increasing the damage, but it doesn't stop you from adding on extras.

Generally, they do not stack with each other or other types of bonuses, only the highest bonus applies.

One of the Talent powers in Power Profiles, meanwhile, specifically mentions being usable with a pistol.

You can launch a virtual whirlwind of attacks against your foes, applying the Multiattack modifier to your attack, up to the rank of the modifier or the attack, whichever is lower. Therefore with 3 ranks in Flurry, you can Multiattack with a light pistol (Damage 3) even though it is normally not capable of Multiattack fire.

The additional damage might not be kosher by strict RAW, but the other extras are... and like you said, it's not exactly game-breaking.

[Cazero]

Or, perhaps, that rule would prevent increasing the damage, but it doesn't stop you from adding on extras.

Ho, right, that. I was wrong.
You can't stack effect ranks of powers with equipment. You can pile up extras just fine.