Since you mentioned having a research system planned, then you should incorporate that into different types of fusion reactor.
The main reason why we do not (as of 2013) have a working, positive gain fusion reactor is lack of knowledge of the specific motion of the fusion plasma in a Tokamak. The ITER (not finished yet) should be large enough to average out most of the instabilities, and supercomputers (like TITAN) are currently being used to attempt to simulate the instabilities to account for them before the ITER is turned on. <-- This is very good for large installations that need to produce and consume large amounts of power, but needs very good computer to run.
The reason why we do not have a Polywell reactor as of 2013 is a combination of lack of funding (we are fairly certain a large enough tokamak will work, polywells are still unconfirmed) and a lack of the required electromagnets needed to generate the field geometry which will contain the electrons in the centre of the chamber, the actual fusion part will be contained electrostatically, which can be done very very easily (can make it work for low power in a bell jar, the problem for higher power is decay of the inner negative grid, hence using contained electrons). <--- This gives good prerequisite technology for propulsion system (see below) but does not scale as well as the above, and requires superconducting electromagnets.
Example: A polywell reactor (electrostatic inertial fusion confinement + magnetic inner electron "grid" confinement) would require more advanced electromagnets (and arrangement thereof) than a Tokamak, but would require much less in the way of computer simulations. Both are scalable, though the Tokamak might be better scaled for extremely large devices, both also have a minimum starting size, though the polywell requires much lower starting energy, and no need for a heating system, just need for a small high voltage power supply to maintain the electric field for acceleration.
Also: the polywell reactor technology will be very applicable to a propulsion system, as utilizing the same electron confinement method one could build a high flux ion drive engine (plasma thruster, but higher specific impulse than the normal kind), and not worry about the current problem of grid decay.
This gives two main types of reactor: The tokamak design for ground based, high power systems and the polywell design for the ship.
