i'm not quite sure where you are going here. now in theory a 120v battery system would pose smaller wires to be needed and it would nearly equal amps dc in to amps ac out plus inverter needs, but then you are locked into buying batteries 10 at a time. another problem is that the controllers are not made for this range of voltages needed to charge such a large voltage battery bank. all this is not worthwhile to somebody with just a few pvs, but may have some theoretical advantage only in the largest of systems. also note that 12v/24v is common to use as some items can bypass the need for higher losses from inverted ac by running direct from the 12v/24v battery bank.
now there may be miscomunication or misnomers going on here, but i'm not seeing the problem let alone a battery problem. can you elaborate more specificly what leads you to believe there is a battery problem.

Its all about NEC regulations, battery banks larger than 48VDC get into some VERY hard to implement safefty requirements, so all the manufactures stay at or below 48VDC ( nominal ) to stay clear of the regulations

A Hi-Voltage DC battery bank is very lethal ...

forgot about that one sg and i believe the cutoff is supposed to be 50v. that is a sticky area when using a 48v system imho as voltages are typically going to be about 54.8v on a fully charged and rested 48v battery bank. individual inspectors may vary on this opinion if it falls under hi voltage or not. most would agree 48v nominal to mean 4 seriesed 12v batteries and not throw in the technicalities. i guess it depends on whether the inspector is not very bright or if he wants to be a jerk about things. come to think of it i'm sure insurance companies would pull this type of a boner even if the inspector passed it.
you are quite right about its lethalness as ac being alternating may allow you to let go whereas dc can cause and hold a muscle contraction more readily.