Imu might be a word play on UMI.
umi = king in hawaian
umi = sea/ocean in japanese

The snake mode could refer to how pythons kill their prey by grappling their target and slowly squeezing them do submission. Would be an interesting fighting technique for luffy and make him more versatile.

His weakness could be, that luffy can eat katakuri body while utilz2din mocho mode. A fleeing katakuri with luffy chasing for a snack.

Believe the following events will occur.
Tsunami to incapacitate sunny.
Crew flee in the subshark before tsunami hits them.
Big mom will find no cake, and kill perospero.

How much mom will go rampage on the kingdom is ???
Battle vs katakuri will not have a winner but luffy will showcase something new.
Why 1vs1 will end is when katakuri realise that big muma rage is the larger threat to his siblings.
He will not fight her but help mugiwaras in some way with the cake.

….
...
...
Mom eats cake and loses conscience.
Mugiwaras are allowed to leave 8n subshark or an allied ship

Tamatebakko chest to explode at the bottom and topple the cake mountain to give our heroes the opening to flee.

Got a feeling the true horror of big mom is about to showcase. White beard level of wow where she rampages out of control and start's eating everyone she sees while weakened by the poison allowing straw hats some fightback. In the end everyone that survives flees through the mirror etc etc and the final scene of big mom in this arc is she sitting alone again wondering where all her children went.

Who is the last one of the 3 Sweet Commanders?

Don't forget that other guests are invited to the Tea Party. We have not yet seen all the guests so far, might be someone of immense power to support luffy.

Expecting the clones to be the solution that our "gas gas" user needs to make the giant army Big MoM wants.

Wonder what it is the germa 66 are after.

This series just gets better and better. Just love it.