How to switch a 700A 200V pulse for a coilgun?
Very fast turn-on is essential here so you need a very powerful gate drive. You don't care so much about ringing etc. So go ahead and pump 10A into each of the gates.
If this is still too slow to protect your FETs, maybe check out some GaN parts which have much lower gate charge.
Another step you can take to slightly delay the current surge until after full turn on is to add a tiny series inductance with the caps. Around 100nH