Hiruzen already has those two things.
With a good amount of stamina, Hiruzen can make at least 20 clones. Kakashi with a 3 in stamina and worn out after his battle with Zabuza was still able to make
You must be registered for see links
from what I can count. We all know that Shadow Clones can be used as
You must be registered for see links
to be able to use RDS multiple times. Fuinjutsu is a great counter to Byakugou as fuinjutsu bypasses her durability. 1 RDS is enough to bypass Byakugou's durability, there is no chance that Tsunade can take on 21+ RDS users when all of Hiruzen's clones are massively superior in Taijutsu and Speed. Which brings me to my next point, Hiruzen's underestimated speed.
Hiruzen has showcased massively superior speed feats than Tsunade, being able to
You must be registered for see links
when headed towards the battlefield. By this panel, Hiruzen's movement speed is on par with Hashirama and Tobirama's movement speed, both who are top tier in speed and easily faster than Tsunade. Hashirama on his feet was able to outrun the Perfect Susanoo and the Kyuubi to the shoreline. Tobirama was able to bypass Obito's senses and tag him, something that not even Amaterasu could do. Hiruzen by scaling his speed to Hashirama and Tobirama is easily one of the fastest characters in the story, much faster than Tsunade.
Hiruzen can also use the formation of the
You must be registered for see links
. This is a variant of the
You must be registered for see links
that the Sound 4 used. All Hiruzen needs to use this is 4 clones. If 4 Chunnin level shinobi can use it, 4 Hokage level clones should also be able to use it. In fact, the Sound 4's barrier would be large enough to trap both Tsunade and Katsuyu. Seeing as how the barrier can tank the Juubi's country buster, Tsunade has no way out of it.
Regarding C-Rank Katon, sure it's weak; but that doesn't mean it can't be used to kill Tsunade. Say Tsunade gets trapped inside Hiruzen's barrier, then Hiruzen can do the following: Set the Place on Fire. You might argue that C-Rank Katon doesn't have enough temperature to even scratch Tsunade, but people fail to realize that Hiruzen has the capabilities of raising the temperature of his Katon: and that is by utulizing his utility and Enma. Metals such as shuriken are great conductors of heat and would greatly raise the temperature of his Katon. What is devastating about this is that the databook says Hiruzen's jutsu allows him to create
1000 Shuriken. 1000 giant Shuriken would massively increase the temperature of his Katon. Not only that, but Enma is diamond. Diamond is also a great conductor of heat. Enma's staff form can also shape-shift into great sizes, allowing it to increase the heat even more. Byakugou has a
You must be registered for see links
. By setting Tsunade's area on fire, she would burn at a constant rate, thus hastening the cell division even faster. Not only that, but by setting the inside of the barrier on fire; all the oxygen molecules around her gone.
More Byakugou weak points? I'd be glad to inform you. A big weakness is that the chakra that supplies Byakugou comes from the
You must be registered for see links
. The shinobi body comprises of
You must be registered for see links
, a few of them are in the forehead area. Sure Hiruzen can't see chakra points, but if he were to sub-consciously strike the chakra point in which her Byakugou releases from, then the jutsu would stop.
Tsunade dies a slow painful death.