Would it be possible to add support for other reactors from other mods such as Space Exploration, Krastorio2 and Plutonium Energy or would this be too cumbersome?

If it looks and acts like a vanilla reactor, should be pretty simple, as long as it burns nuclear fuel of some kind.
And if it doesn't, the control interface probably isn't necessary anyway.

FYI, this isn't true by default. The list of reactors that the mod interacts with is hard-coded to be:

reactor_names =
{
  ["nuclear-reactor"] = true,
  ["nuclear-reactor-2"] = true,
  ["nuclear-reactor-3"] = true,
}

You can add more reactors that use burner fuel to this list, like "se-antimatter-reactor". The mod could easily be modified to work with any entity of type "reactor".

Well yes, I did say that it would be simple to add, not that I had already done so :p

I'm not sure whether it's better to have a hardcoded list of reactor types it makes sense to use the control interface with, or make it automatically apply to any reactor-type entity. For example I know Nullius uses type=reactor for things like the geothermal and solar thermal power plants as well.

Maybe I could check for both type=reactor AND energy_source.type=burner (and/or energy_source.fuel_category = "nuclear"), but that gets a bit complicated, and really what matters is that the entity's sprite is based on the vanilla reactor sprite so that the interface fits visually.

So maybe a hardcoded list of compatible reactor-type entities is best. Just post the entity names that need to be added to the list and I can do that.

I'll go ahead and add K2 & SE since I'm familiar with those, others will have to tell me about other mods.