hahaha, i can not stop laughing, so cute this slug sage. if it really happens, it will be so so awesome in naruto!!!
BTW, awesome job!
Can we really rule out a Tsunade Slug Sage? I don't think so. Like the other Sannin, I think she will have an incomplete Sage Mode. Both Jiraiya's and Orochimaru's underlings mastered their sage mode(assuming Kabuto has done so..................It might make an Opening for a Sasuke Dragon Sage Mode if Kabuto is incomplete, allowing for a Sakura Slug Sage to complete the trifecta for team 7).
Either ways, either Tsunade has it or she doesn't, but I'm sure that unless the Uchiha Bros. stop the Edo tensei, Tsunade will have to go all out, and, if she has some Sage mode, she'll have to use it to stay alive. Unless, she has to die, in which case, she could finish her story with the Shiki Fuujin.
Tsunade is already a shinobi not to be trifled with! I like how awesome Kishi is making her out to be, stronger than even the Raikage. Sadly, it just so happens that she's facing the beast which is Madara, lol, along with upgrades such as immortality and the real upgrade, which is the attainment of Hashirama's power to add to his own, which is equally as impressive in and of itself.
But back to Sakura, the only thing she needs, is to master the Genesis Rebirth technique, so that she doesn't have to worry about getting killed in battle, and can bring havoc to most opponents without fear of retaliation.
Now that you mention it, I do suspect that Tsunade has the requirements for Mastering Sage Mode. She is part Uzumaki, and has a very large chakra pool, whether it is stored in her forehead gem or not. However, it would be surprising for Her to suddenly bring out Sage Mode now, when she didn't use it before, during the Pain invasion.
I am not perfect and I defy you to prove otherwise
Growing Old Gracefully is an Oxymoron ... Mostly Moron !
Naruto has become after mastering it .