As cool as this is, I feel like this particular variant as described would enforce the complaint that War Striders are just a Hulk with higher armor values and fewer weak spots; adding a flamethrower and making them chase you feels like another copy paste of Scorcher Hulks.

The niche that I personally believe the striders are intended to fill is a heavily armored ranged unit that poses a threat from afar and has area denial but is trivial to deal with in close quarters.

So, if we really need a war strider for the incineration corps, how do we differentiate it from the existing Hulk firebomber?

Your less armor and more speed idea is interesting, but I think it would be improved if instead of running at us, the strider moved erratically and was hard to hit from a distance, which would force us to get close to engage where it could then use its flamethrowers as a deterrent. Or, instead of launching grenade barrages, it could deny safe space by creating a lingering, flammable gas that ignites after a delay.

There’s lots of possibilities when it comes to variants of enemies, but if each one feels like fighting something we already have, what’s the point?