Buying better thrusters will make it more maneuverable, and better shields will make it a bit more survivable, but there is only 1 weapons slot, so your firepower is very limited no matter what you do.
The base ship just isn't made for this, but a fully upgraded hauler would be a laugh to surprise some people with.
The viper is about the same size as the hauler and the standard version is much cheaper than getting the upgrades on the hauler would cost. Maximizing the cargo capacity of the viper may get you what you are looking at, but if you really want a transporter / fighter, its hard to look past the cobra