Connecting batteries in parallel (concerns)
It is very common to connect lead-acid batteries in parallel to increase capacity.

A common house battery bank on pleasure boats consists of four or more, 6 volt "golf cart" batteries connected in series/parallel to make a 12 volt battery bank.  There is no need for diodes or other isolation between batteries.

Some people express concern that a shorted cell in one battery will cause overheating of the wireing, but I have had a couple of cases of a shorted cell with no problem other than being unable to fully charge the bank.

I have no experience with LiFe batteries.