You can thank the MMX in part for the continued existence of the FX; the MMX apparently is the response to a contract requirement to bring a bike from fully depleted to ready to ride with full energy in less than 60 seconds.
That's a nice line for Zero to use for marketing, but its not true. Every model of the X line had fast swapable batteries, even since before the company was called Zero. It could be that their waterproofing techniques improved because of the MMX.
Well, hence "in part".
You're right that Zero has used removable batteries for their dirt bikes since they started selling the Electricross Drift in 2006-2007. I definitely didn't mean that the removable batteries were invented for the military contract; but rather that a need for a fast swap platform is part of what justifies the existence of the X line.
Consider:
- the XU ran from 2011-2013, presumably axed due to low sales
- the X has struggled with identity between dirt-only, dirt and street models, street, before being reborn as the FX in 2013.
- the MX similarly struggled with identity and mission. It's all but dead now save for fleet sales.
- the FX has seen intermittent updates over the years. It got the unified dash, headlights and pillion seating in 2014; ABS, tires and suspension in 2015 (but missed the battery bump); updated cells in 2016 (but missed the Charge Tank and IPM motor).
- the FXS is a first party supermoto, but the significant change is the IPM motor. Wheels, brakes, tires are from existing bikes.
The X platform isn't dead, but it has struggled to find a niche since the platform's inception, in a way that the S and DS bikes have not. It's good to see Zero continuing to offer some updates for the bike .. but without the MMX or other fleet sales (who do you think buys the accessory QuiQ chargers?), I think Zero would consider offering a smaller monolith fixed battery (at reduced weight and cost).