Some interesting stuff. But... a separation range of 150,000 km for a submunition without a drive means they separate at 150,000 km from the target and never get there. The orbital bombs as linked won't reach their target.
2,400 km/s is a bit slow for Ion, but stealthy standoff bomber is still an interesting role. However, dropping to 3 engines, more boost, and an extra 50,000 liters of fuel would likely give you both more speed and more range.
The biggest problem is that their weapon range far exceeds their fire control. You would have to fire it at a waypoint and hope that an enemy will be within the sensor range of the missile. 2-stage missiles fired at waypoints are very vulnerable to AMMs hitting them before separation.
Having short crew endurance but long maintenance endurance is decent for manned colony defense.
I like the Predator Slash. The range it can home in on a target is decent, enough to interdict a small moon system. I wouldn't use it against anything with a point defense system, but I could see it being very good for harassing civilian shipping. You could fire on a ship as it loads or unloads cargo at a colony, when it could be counted on to be stationary long enough, and the shock damage from the large warhead would be a significant increase in damage.
I suggest that you design a strike group instead of small ships that operate independently. Build sensor variants, and use the saved HS to get a large, long ranged missile fire control. With the ability to strike an enemy from outside their own effective missile range, you have a classic strike weapon system.
