I was traveling in Japan and a taxi used 20+ USB outlets, mobile wifi and multiple device charging.
He upgraded the wire from the battery so it could handle all the devices. He had two wires from the battery. The regular wire to the charger was not good enough. Each gadget draws perhaps 2 amps he was using almost 30 outlets. 40-60 Amps of toal fuses would be enough to handle them (and their spiking current demands when you first plug them in or turn them on).
Here is the picture which shows about 14 Cigarette chargers and nearly 30 USB ports.
It is likely that a battery upgrade was needed to get more amp-hours and to allow for heavier non-starter usage of the battery.
Amazon has the Optima Blue top deep cycle battery. It has 750 cranking amps to ensure a reliable start and 55 amp hours for more device capability. ($180) A typical car battery has 20-30 amp hours.
There is a six USB port for one cigarette port. The jelly combo has 65W 13A rapid charging. It supports up to 6 power-hungry devices with their maximum charging speed while driving.