Normally, incapacitated heroes can't use powers at all, even if they have one from some source other than their own cards, because the rules say that the only thing they can do during their turn is use an incapacitated ability. The rules don't actually say they have no "use a power" phase. So could you conceivably use, say, Infection and Embolden, to give an incapacitated hero a power use? What about Cosmic Weapon and Dynamic Syphon? (In fact, it seems those can even be played directly on an incapacitated hero. Not that this would normally be a good idea.)
And if that works, I just ran across this in the clarifications:
"If Embolden is on a hero and that hero becomes incapacitated, Embolden stays there until the end of that hero’s next turn."
Presumably, this is because you can't deal damage to an incapacitated hero--unless they're Huge Skyscaper. That could be a highly amusing workaround.
Well the video game is the easiest item I can point to. An incap hero has a start of turn, incap power, and end of turn phases listed. I'll check the rule book too as there should be something there.
In the Enhanced Edition rule book on page 7 it talks about Incapped heroes and says the only thing they can do is use one of the three abilities on the flipped side of their character card.
Sky-Scraper does not have a power phase, but can use powers. You just need Captain Cosmic to give her a power.
Incapped Sky-Scraper remains a hero character card, and when she is a target, she can deal damage. So you can Dynamic Syphon Incapped Huge Sky-Scraper and give her a cosmic weapon and she will be able to use that power if she is a target when Cynamic Syphon gives her a power use. Wounding Buffer is a popular construct to put on incapped Sky-Sraper in my group.
I haven't tested this in the app, but by rule it should work.
Attached Wounding Buffer, Dynamic Siphon, and Cosmic Weapon to incapped Huge Sky-Scraper. Used the incap ability to be a 1 HP indestructible target. Had one damage dealt to all hero targets during the environment turn. Wounding Buffer reacted when Sky-Scraper was hit but when Dynamic Siphon was hit no prompt to use a power happened.
I wonder if here is an unstated requirement to be an active hero attached to using of powers. That makes the most sense, either that or they didn't think of it.
I submitted a ticket through the alpha testing about the Dynamic Siphon and Cosmic Weapon in a 1Hp incapped Sky-Scraper. Might be a while for a response from Christopher on it since I have to imagine the Handelabra team will take a bit of a break after releasing Vengeance.
If you want an answer on an incapped huge Sky-Scraper as a 1HP with Dynamic Siphon attached using the power on Cosmic Weapon you'll have to ask Christopher directly.
Like many SOTM rules questions, might the answer to this be in the wording? Just like there is a difference between "playing a card" and "putting a card into play," it seems to me that "incap abilities" are not "powers." Therefore, incapped heroes don't have a "power" phase; they have an "incap abilities" phase. So, (a) if Dynamic Syphon was on an incapped Sky-scraper, it wouldn't do anything because the Syphon allows a hero to use a "power," not an "incap ability"; and (b) even if Sky-scraper had a "power" to play (such as by having Cosmic Weapon on her), she couldn't play it, she doesn't have a "power" phase in which to play powers, only an "incap abilities" phase. Does that make sense?