It repeat after me: only needs a "great deal of development" because of safety concerns. Lock some engineers in a room overnight and tell them to build a reactor with zero safety concerns and it will be quite simple. I'm not terribly familiar with breeder technology but it cannot possibly be remotely as expensive as uranium centrifuging. Here's my breeder reactor design and I'm 70% sure it'll work despite my knowing almost nothing: aerosolize the U238 or other isotope-to-transmute of choice. Set up a convection system that thoroughly mixes and circulates the powder near your neutron source--this could be done in a relatively neutron-transparent liquid or (maybe) a gas. Set up your neutron detectors and thermal imaging all around the area. When fission rates increase and/or when it starts looking hot, your neutron source retracts into its safety chamber and a series of fans blows away any residue dust off of it. Resulting powder is measured and melted or compressed into appropriate ingots for fuel usage. If it's going too slow, increase rate of neutron flow. If it's too fast, reduce it. If it's so fast that it blows up, oh well, stuff blows up with oil and coal all the time. None of this is prohibitively expensive unless/until you try to make it super safe.
By that design principles, I have three better proposals: First, lets go to fusion directly. We only need to set up a containment field for Deuterium plasma, heat the plasma with lasers until there is ignition, and then keep running the plasma through an magnetohydrodynamic generator which we can also use (with some tricks) to separate out the fusion products (heavier nucleus = less deviation in the electric or magnetic field). Easy peasy! Or we could go to an antimatter reactor - just feed hydrogen and antihydrogen into the reactor core in a controlled manner, and use the trilithium crystals to convert the resulting gamma- and neutrino flux to usable energy. The last option, and maybe the best one, would be a perpetuum mobile. I have a design with magnets and a wheel with paddles on hinges that only needs a little tinkering before it becomes a better-than-unity device!
More seriously, have you considered the problem of induced radioactivity? Everything in your reactor with be "hot", so that it will be extremely hard to do maintenance. Most sensors will not work well when constantly bombarded with neutrons and various forms of radiation - and neither will computers. Indeed, any serious neutron flux will make most construction material brittle over time, so they need extremely careful selection on materials, careful monitoring (with sensors being susceptible to radiation damage themselves, as stated above) and frequent replacement - leaving you with a heap of radioactive waste.
There may be reasons to consider nuclear to be better than coal, but it's not remotely as simple. To use an analogy, we don't have to chose buying "protection" from Luigi or from Guido - we can just invest in a working society with a working police force. It may be a little bit more expensive in the short term, but it has plenty of secondary advantages, and certainly is cheaper in the long term.