Maybe they could convert medium and smaller ships to nuclear power? Aircraft are going to be difficult to decarbonize no matter what way you slice it. I think AbramsX was already looking at a piston engine instead of a turbine to decrease fuel consumption.
It would be very cool, but using an unshelled nuclear core as a heat source for a ram jet has some pretty bad radiation side effects for the air going though it.
I was talking about the shielded core version, and with non nuclear warheads, basically it would specialize in being fast as all fuck and having cheap munitions to shoot missiles out of the air with.
More importantly, making it public that you're dismantling warheads to achieve this, make a display of exiting the nuclear arms race by developing a tool meant to pose a direct challenge to nuclear hegemony.