Yes, this is possible. But it prevents you using all of the advanced features of the QSPI. Using its own chip-selects you can load the QSPI RAM with up to 16 transfers to different chips and let it run all of them automatically. To use a GPIO instead of a chip select the driver has to program one transfer only in the QSPI RAM, and then assert and deassert the chip select around that transfer.
If you're not using these features and don't need the efficiency, CPU offloading and speed, then it doesn't matter.
It might be better to swap spare GPIOs with any of the QSPI Chip Selects that are being used as GPIOs.
Also, if you can free up one chip-select, to have two QSPI CS pins, then you can use an external address decoder to generate three chip-selects. Or three pins to generate seven chip-selects.
Tom