We don't really know for sure that Isshin regained his powers because of Ichigo's influence. We know that Orihime and Chad awakened their latent powers because of him -- or rather, since the Shun Shun Rikka, Orihime's powers, told her so, I'd say we can definitely say for sure that Orihime's were definitely awakened because of Ichigo.

All we know about Isshin's power restoration, is that he didn't start to actually try to regain his powers until after he realized that Ichigo has met Rukia and taken her powers. He started trying to regain his powers after that, and once he started trying, it only took him maybe a month to a year, or less. But he'd already been powerless for twenty years. And chances are that he, too, used the FGT. If so, and I'm right about all of what I've just said concerning Isshin, then this means that Ichigo can get his powers back in a way similar to how Isshin regained his powers. Urahara and/or Isshin might help him, and/or maybe this new guy with the Shinigami Badge could also have a hand in it.

As I've said before, that "ability" is something all great warriors probably have, one that lets them read their opponents and their emotions during battle. I've noticed Kenshin being able to do this in the manga Rurouni Kenshin, too. And I bet that all Captains are able to do it, as well. They're high-level fighters. You're right that trying to assess the situation during battle is hard, but we've seen characters other than Ichigo also be able to fight while analyzing the battle, like Uryuu, and to a degree, Ukitake and Shunsui. Ichigo isn't able to do it to a level on par with theirs. And we're not talking about that particular ability anyway. It's different from being able to read an opponent and tell how they feel or whatever. Ichigo can do it with Plotkai. I don't know, it may be possible to "sense" someone's feelings within his/her spiritual energy aura? Ichigo was never that good and sensing, so maybe, if he learns to be better at it, and also learns to fully control his power, he wouldn't need to use Plotkai.

Plotkai - Ichigo