ISL81801 reverse-direction response-time (HOLD-UP Application)

I'm planning to use the ISL81801 as a hold-up function, but are starting to doubt if it is useful for this, due to its very long forced minimum Soft-start of ~1.7ms.

1) When the voltage is above 35V, external logic will enable the charging from ISL81801-INPUT to a capacitor bank 150µF on the OUTPUT side. The product typically will use up to 500mA @30V or 250mA@60V (15W)

2) The charging is held back by an external control loop to make sure the charging does not pull the input voltage lower than 35V. This is done by manipulating the FB_pin on the output side of the ISL81801.

3) When the Capacitor bank has charged to 70V, the charging stops, but the controller is still enabled as long as VIN>35V.

4) During a dip of the input-voltage to the product, slightly below 32V, we will enable the controller and WILL NEED INSTANT HOLD-UP POWER from the Capacitor Bank. The ISL81801 will need to initiate immediate REVERSE power-delivery to the input (which at this point is pre-biased to marginally below 32V; lets say 31.9V as an example.)

Q1: Will the activation of this reverse power-delivery be possible, without being forced to wait for the 1.7ms minimum soft-start? (Which would render the whole solution meaningless). 

Q2: Do you have another, more efficient way of using the ISL81801, that better will support the described functionality?

Additional background/context:
The product has a power input through at very long cable with significant inductance and resistance in the path.

Due to this the 60V power source may show up as anything between 30 and 60V on the input of the product during steady power consumpton.

The power-supply will handle the 30V-60V range, but will need a hold-up -function to support the input during temporary spikes / step-loads in the current consumption.