[x] Try and improve on her Sealing by working on her Lightning Blood Seal.
The Lightning Blood Seal is awesome, but also has significant flaws, flaws which have been pointed on film. There's a very reasonable chance that the next significant fight we'll have will be against someone who is aware of these flaws, and will try to take advantage of them. Let's make sure they are the ones who receive a nasty surprise, rather than us.
[x] Work out the last problems with her Beast Slaying Vacuum Talon.
The other significantly flawed yet highly important part of our arsenal. Whereas Lightning Blood Seal just generally makes us a lot more capable, Beast Slaying Vacuum Talon is more of a... problem-solving tool. It's usually not relevant to our combat performance, until we encounter a problem that can only be solved by using it. In fact, there are many times where BSVT isn't just "the best solution", but "the only solution". We cannot afford for it to have significant flaws that can be taken advantage of, or we will eventually encounter a situation where it bites us in the ass.
[x] Try and improve her taijutsu by training with Gai and Lee.
I'm reasonably split between this and researching the Chakra Armor, and think there's really good arguments for both. Taijutsu is a weakness of ours that will inevitably need to be patched up, and Gai and Lee are pretty ideal people to train with. I wouldn't be surprised if this would also up our speed.
Also, Gai and Lee are wonderful, and I want to see Hisana interact with her fellow "genius of hard work".
As for the chakra armor, though, I'm interested in it for other reasons than to just have chakra armor ourselves. Its kind of a "mystery box" research-wise: we don't really know what we might learn from it, but for all we know, principles from it could be used to significantly improve certain aspects of our Sealing. We won't know until we try.
Another thing I think people are overlooking about researching chakra armor is the fact that we have enemies that will be using it, and by studying it, we become better able to defeat those enemies. Chakra armor has gaping flaws that our allies were able to take advantage of, and it would be nice for us to be able to do that as well.
Still, I feel like the "Taijutsu with Lee and Gai" is the more time sensitive option compared to studying chakra armor, and I think it is greater in importance.
...One thing I will mention, though, is that I may be underestimating how much getting the Sword of Spring devalues "develop Beast Slaying Vacuum Talon" and "learn Taijutsu" as options. A sword that can reform itself does fix a significant problem with Beast Slaying Vacuum Talon, and it means there's one less way we could be forced to fight with Taijutsu rather than Kenjutsu. I will think more on this: perhaps I'll change my vote later.