you System with three Independent MP2 does make sense.
The 3p HMT need a synchronize 3p cluster of MP2.
Create a 3p cluster of MP2s.
Connect all batteries parallel and as one stack.
Connect the MP2 cluster via common DC bus bar with the batterie stack.
Connect MPPTs to the same DC bus bar.
I recommend using two couple Lynx Distributors.
If you haven’t bought the batteries, consider NKON ESS Pro or other 16 kWh. In any case go for 16s.