What unfortunate side effects am I missing in allowing a feint as part of movement at a -10 penalty?

Question

Within Mutants and Masterminds, if you have a feat called Acrobatic Bluff (Agile Feint in 3E), you can use an Acrobatics check in place of Bluff (Deceive in 3E) for the purpose of feinting to make someone flat-footed for your next attack. It is, by default, a Standard action, but the game allows you to do it as a Move action with a -5 penalty (which in 2E can be countered by a 1 PP Challenge Feat to remove that penalty). Obviously, making it a Free action for a -10 penalty can cause issues with the action economy since it's essentially cost-free (other than possibly racking up the -1 penalties to subsequent attempts against the opponent in 2E), but one of the iconic moves in the comic books is the agile gymnast doing a series of handsprings and cartwheels across the floor to confuse the opponent before striking (c.f. Harley Quinn in many of her performances).

How would allowing an Acrobatic Bluff check at a -10 penalty for doing it as part of movement break the system? Obviously, someone with a high enough bonus might be able to consistently overcome the penalty (particularly if the GM lets them buy off the penalties with Challenge Feats) and there's some risk of people doing it all of the time "just because", but it seems largely reasonable to me. Am I missing anything other than that it isn't in the book already?

I posed the same question on the Atomic Think Tank and the point was raised that the Charge action is a Standard action where you can move 30 feet and attack. Doing the Acrobatic Bluff as a Move action at the beginning and then doing a Charge is a viable action here, it seems. It feels really strange to me since mechanically it works out as "let me distract you by doing a backflip and then run straight at you and attack!" but it does achieve a similar effect and only with slight modifications to attack and defense bonuses (in 2E, +2 to attack and -2 to defense. In 3E, -2 to attack).

Answer 1

The biggest reason is that, as you have stated, it is primarily useful against people who are defense-shifted.

There's already a bias in the game towards toughness shifted characters since Area attacks bypass your active defenses (which isn't quite offset by the fact that active defense don't degrade as they're beaten, like toughness does).

The biggest issue that I can see is that it would let a damage-shifted character bypass the active defenses of a defense-shifted character much more easily and avoid the PL-limit imposed on Area attacks.

So an acrobatic tank could have a +20 bonus to Acrobatics and routinely make a d20 + 10 roll against a defense-shifted character's Insight/Acrobatics roll. A defense-shifted character would thus have to be either almost as acrobatic (+10 bonus or better) or extremely insightful (+10 bonus or better) to have a 50% chance to not be flat-footed.

It's an understandable thing, I think - granting the flat-footed condition as a skill check is a relatively potent thing. How badly it affects your game depends on how many defense-shifted characters there are.

Keep in mind that your player's character can always use the Set-Up advantage to transfer the flat-footed condition's benefit to another character. It's much more in-line with how comic combat works, and it actively engages characters in working together.