The way I see this match up is pretty much the same way I see how Gokage was treated against Edo Madara. Gokage's were able to push Edo Madara to use his strongest move in order to wipe them off. These Edo Kage's could put Hashirama in the same corner, but not being able to activate his full power is where things go into question.
Then again Edo Kages only share like 40% percent of Gokages arsenal. Let me see if I am convince Hashirama doesn't need SM:
With Muu Fission (which works faster then Clones) he should be able to multitask the beginning of the fight by lightening 2 characters for an effective strategy. 1) Being Ei and 2) Being Genjutsu along with summoning (Clam).
1.) Backpack Ei was able to force Madara to defend against his attack. This Ei (3rd) has different attack that is base on penetration via Nukite so Hashirama will be force to use Mokuton as protection/escape. The speed of the attack, at the end of the day, buys time for Clam to be set up.
2.) Clam being activated, only has one factor, and is confusing Hashirama with Illusions/Mirages. One could argue Hashirama can locate the Clam on the ground, but the strategy is difficult here base on the fact that Muu is able to make it fly out of Mokuton range (and Hashirama himself). Plus the fact that this Clam can nullify the opponents use of sensory.
Hashirama would basically be stuck in a loop here. As his sensory is nullified and mirages of all the Gokages, will effectively fool him into attacking and countering the real ones.
Genjutsu would be with Clam, flying around, maybe sniping with Water Gun? Joki boi would be running around the field, pressuring him with Kamekaze's and forcing Hashirama to shield. Raikage can Juggernaut in at anytime with 1 finger Nukite and back-stab. Muu's Jinton snipe can't be detected. Rasa can be much of a support much like Gaara, idk.
I would like to see how SM isnt needed here.