Does the AUS Grenadier with a steel bumper, but without a winch, have the same front springs as the UK Grenadier with a plastic bumper, also without a winch?
If the answer to that question is "Yes" - then if you purchase an AUS Grenadier with the steel bumper, and you add a winch later, then you are adding much more than just the weight of the winch, you've got the bumper as well.
Adding both a steel bumper and a winch (as weight in front of the front axle), without increasing the load-rating of the front springs, will be very noticeable, and will degrade handling of the vehicle. It is not equivalent to carrying the same weight in the passenger compartment (i.e. between the two axles).
Maybe Ineos has developed multiple spring rates for the different variants of the Grenadier. They wouldn't need all eight of these options (below), as there will be some cross-over in weight between some variants. In other words, the eight options listed below do not represent eight distinct weight-classes, but they certainly represent more than two.
1. Gas engine / plastic bumper / no winch - lightest vehicle
2. Gas engine / plastic bumper / winch
3. Gas engine / steel bumper / no winch
4. Gas engine / steel bumper / winch
5. Diesel engine / plastic bumper / no winch
6. Diesel engine / plastic bumper / winch
7. Diesel engine / steel bumper / no winch
8. Diesel engine / steel bumper / winch - heaviest vehicle
Does anyone know how many front spring variants Ineos has developed? Just for comparison - Ram Heavy Duty trucks have dozens of different front springs, based on engine, bumper, payload, snow-plow package, and winch options.