Non-monotonic rise on the power supply

That’s not a good idea. The power supply rise requirement is not just for successful configuration. During the power up ramp, the device has several reset and initialization stages (not to be confused with the post configuration initialization cycle). These are voltage level triggered events. If the VCCINT rise is non-monotonic, meaning it rises, falls, the rises again, these power up sequences can get corrupted and the device may fail to function properly. You really need to put the effort in your power supply to assure a monotonic rise