It all seems generally dubious to me. But I think solar panels could survive that force if they were firmly supported inside the vehicle before launch; I don't

It all seems generally dubious to me. But I think solar panels could survive that force if they were firmly supported inside the vehicle before launch; I don't think the acceleration itself would break the panels if they were prevented from flexing. For an engine, maybe solid fuel but the fuel itself would be structural. A pressure-fed liquid fuel engine might be easier, if you could get valves (and actuators for those valves) to survive that kind of force.