I would also stay with the 60c rating. You could, as an alternative to 4/0, possibly use dual pairs of 2/0 cable from each battery terminal-connected bus. The paired cables would have extra capacity, in comparison to maximum input current of your "2000w rated" Inverter.
If high current does occur, you might have an issue with the BMS of the single "200Ah" battery. But the cables to the inverter would not be an issue.
If high current does occur, you might have an issue with the BMS of the single "200Ah" battery. But the cables to the inverter would not be an issue.