This technique shall get nerfed. It is too overpowered and on the same par as a Bijuu. However, if this technique shall get legalized on usage to Shinobi Legends' RP World, then I for one, would say that the Perfect Susanoo should be added/legalized just as much (though, it is nerfed as well). It doesn't really make any sense if this technique is legalized on usage in RP while Perfect Susanoo is not.
Perfect Susanoo would only require 4 Uchiha resets + EMS.
This new Mokuton technique may be pretty powerful, but it requires a total of 10 resets in order to fully utilize it (4 Mokuton, 6 Sage Mode). Sure it may be able to restrain a tailed-beast, but I'm sure a jinchurikki would be smart enough to not go full bijuu transformation, to only get caught in it. They could just remain in their normal state and still have the perks of a truly massive chakra supply.
It seems pretty fair to me, since the Rinnegan can pretty much defy and control some of the laws of life and nature, even at the bare minimum of 2 Uchiha resets, 1 Mokuton reset and 1 Rinnegan reset (4 resets minimum) + EMS.
But we also have to remember that this is a true kage-level battle. So it's not like everyone on the site is going to be able to do all this.
Honestly I'd say that this is far more than a 'kage' level battle. This is a battle between two absolute legends xD
Considering the 1st hokage is moving on his own while under the strengthened edo tensei like it isn't even a thing and the rest of them are trapped. (Although my bet is because he had to use Hashirama's cells to strengthen it, and well, he IS Hashirama so he controls them better xD)
I don't even think that the majority of Kage's on SL would rank within this power level (or that they should really)
In all technicality, all Senju in SL have vitality and the potential for Mokuton. Though those with Mokuton of course have the superior vitality. But it's not too much to worry about, since among the kages, only Zen and myself have the ability to use this massive Biju-stomping jutsu. But you won't see me going around and spamming it in every village and battle I come across. It's just not in my character to do such a thing.
The only thing one would really have to worry about, is someone who is more than willing to do that. But that's the whole point of being/having a kage. To take on the most dire and serious of threats that attempt to trample upon the village they serve and maintain. But that doesn't happen at all anymore, since apparently almost every village has impenetrable/indestructible/invincible/inconceivable/incomprehensible/illogical/inconsiderate/incoherent gates and walls which either limit or restrict RP
heavily. But that's a whole other issue for a whole other thread to discuss.