I figured the same thing. My 5th wheel didn't have any battery dissconnect switch installed. So, I Installed a 50A unit for the trailer system and a 150A to my 1000w inverter. Seems to work well. Haven't tested actual overload conditions. Size appropriatly for your wire size.
If to replace the mini circuit breakers in the tongue area, that might be a good idea. I don't like that the stock breakers in the tongue area are self-resetting. If you accidentally connect the battery(s) in reverse, it will keep resetting and eventually kill the battery(s) which is what in some friend's TT last year.