1. 2kg is 4.4lbs. Just give a total weight, number of people, and height that it can accommodate.
Also, move this to Appearance.
2. Rockets only need to go 7.9km/s (4.9mi/s) to leave Earth, that's 20x more than the speed of sound. At 3.5k mph it takes approximately 150 seconds to leave Earth, that's 2.5 minutes.
3. Make it that each gun fires 5 beams for a total of 10 per post. And that they each hold 50 shots for a total of 100.
4. Lower the defense health to 400.
5. Your cost:
500 for speed
1,000 for weapons
500 for defense
500 for hyperdrive
1,000 for initial time off
2,500 for hyperdrive time off
2,000 for ammo
= 8,000 Zeni