Then it sounds like the speed isn't the issue, its the flight model itself that is the problem. Maintaining high speed while being able to manouver should be a possibility.
The acceleration the ships would need to be able to achieve would be absurd. They already pull 20g's or something like that and you already think it is ridiculous.
When SC had a separate "cruise" mode the base ship speeds where quite a bit slower than elite. That all changed in 3.5.