New Lithium Bank

I am upgrading my battery banks and want to know if I am missing something.

Currently: I have 3 banks, generator starting battery completely, engine bank #1 and engine bank #2. They are charged by a 3 bank charger. Engine bank #1 & #2 are wired for house use as Batt #1 & Batt #2. So I can use #1 or #2 or Both depending on selector knob.

Plan: I am looking to get 2 LiFePo 200 AH in parallel to Batt #1. Join Engine Bank #1 & #2 to Batt #2. The future plan is for solar to charge LiFePo bank, currently it will have a 40 amp 120v charger. We intend to use generator a few hours a day minimum for appliances and hot water. The majority of boat is setup for 12v usage, lights, electronics chargers, DC fridge and a couple small inverters for TV and Starlink.

Question: I assume I should not run with both Batt banks combined, either LiFePo bank or Engine Bank? I was thinking to install a 12v charger to the engine bank to charge the LiFePo bank when underway.

I am a little confused but yes never should you combine the lithium with another bank. You could use a buck/boost DC to DC to charge your LFP bank from your eng.batteries while running (assuming you are charging them from your alternator). If you could sketch a diagram that would help.