I'll be keeping an eye on this but I have been a big proponent of generators like fusion needing some pretty extensive external setup from the actual block.
First things that come to mind that you could do is building an external longitudinal and latitudinal copper coils out of copper blocks. Obviously then you'd need to look into how to program the entity that would be the Plasma spinning around in it and could probably do some cool stuff with being able to visually show how hot the plasma is. As well you could have it produce more energy and need more fuel depending on how big you make the magnetic coils and how well built they are. For example, Square coils would be easier and still working but not able to produce as much energy compared to a well built more circular coils.
Another kind of nifty thing you might be able to do is shielding it from sending out damaging waves by surrounding the whole thing with Reinforced Stone or some other shielding material, maybe even have it erode over time so that every once and awhile you have to shut it down and rebuild the shielding.
This way you would also be able to have the heating Coils be actual blocks that you have to figure out how to situate them in the field to make them most effective while still being able to wire them up to whatever power and any redstone controls.
The final thing that I can think of is having a way to make it so tat the power produced doesn't come from the field directly but from a water system that you have to set up to flow through it, heat up, and then passing over a watermill/special turbine before passing back through the plasma field again. Something similar to BuildCrafts liquid pipes except able to somehow react to the heat generated by the plasma to move the water through it faster the hotter it is.
My main point is that this is a Fusion reactor, it should be a big endeavor to not only create the technology to accomplish it but as well to build the big ass structure that it aught to require.