A neutron is not stable when it is removed from a nucleus; it decays into an electron, a proton, and an antineutrino. To consider a neutron an independent entity in its own right is inappropriate, since it appears to consist of other stable and less energetic particles.

I don't know Solid State Universe's electromagnetic-based theory, but here's my own (after a little background). It allows for electromagnetic and gravitational forces but not the weak and strong forces.

EVERY subatomic particle that has been physically detected is either an electron, positron, proton, antiproton, neutrino, antineutrino, or photon (which is its own antiparticle), or an unstable combination of those. There are no exceptions.

Quarks and antiquarks have never been (to my knowledge) physically observed, but all of the others above have been separately detected and measured. Some deep inelastic scattering results indicate charges are one-third (or a multiple of one-third) of what they should be, while elastic scattering at lower energies show the charges to be normal. Quarks are used to account for these deep inelastic scattering results that don't agree with Coulomb's Law. That is done by modeling the proton as an assemblage of three quarks, two Up quarks (each with charge +2/3) and one Down quark with a charge of -1/3.

Then it becomes necessary to explain how these three quarks are held together as one proton, which itself is a completely stable particle when separated from all other matter. The strong force is used to explain a proton's stability and the stability of atomic nuclei. Rudimentary quantum mechanics explains forces in terms of force-carrying particles rather than fields, so gluons are added to the model as carriers of the strong force. Electromagnetic force is carried by photons in that model, and some radioactive decay is explained by a weak nuclear force carried by W and Z bosons. Gravity is carried by gravitons in that model. This is my simplified attempt to explain some of the Standard Model in its basic form. Being simplified, it leaves out a whole lot but hopefully isn't misleading.

So the main tasks that must be done in order to create an electromagnetic alternative to the Standard Model are the following:

1. Provide a testable electromagnetic model of the electron, positron, proton, and antiproton in electromagnetic terms. I've done that (see A new model...). Photons are purely electromagnetic, so they don't have to be redefined. That leaves neutrinos, antineutrinos, quarks, and gluons to be explained electromagnetically. Plus the weak and strong forces, and if you REALLY want to get rid of it, gravity.

2. Show that tests support the model in (1). Someone else will hopefully perform valid testing of my model. Anyone else's model would need to be tested as well.

3. Explain in electromagnetic terms the results of deep inelastic scattering. My model (1 above) results in particles that appear to have a charge of 1 from a distance but a charge of 1/3 at their radius (plus or minus charge depending on the particle). Remodeling deep inelastic scattering results, using a modified Rutherford scattering formula with my particle model, could result in a completely electromagnetic match between theory and experiment. That would result in support for the electromagnetic proton model in (1) and would drop the need for Up and Down quarks and gluons as they relate to the proton. The evidence for other quarks would have to be explained electromagnetically, as well.

4. Explain how a neutron or antineutron is held together electromagnetically and explain its mass, spin, charge of 0, and magnetic moment. I might never work on that problem to its completion. I can, however, explain the neutron's charge, and explain its observed magnetic moment in reasonably simple terms with my electron and proton models with an accuracy of 0.999864330. That analysis provides some clues regarding how the neutron can be electromagnetically structured. If modeled electromagnetically, that would eliminate the primary evidence for the weak force.

5. Explain neutrinos and antineutrinos in electromagnetic terms. I have two possible explanations. They could be, as someone else has stated, partial photons that do not conform to E=hf and therefore do not normally get absorbed by electrons, protons, their antiparticles, or composite particles. Alternatively they could be pure kinetic energy. My current speculative model of a neutron includes some funky (technical term) internal movement and an interaction with surrounding space that causes the center of mass to move in a loop. That could lead to linear movement of the center of mass when a proton breaks apart.

6. Explain how atomic nuclei can be held together electromagnetically. That would eliminate the need for the strong force. My belief is that the modified coulomb field of electrons and protons in my model, plus some coulombic inbalances within neutrons, change the electromagnetic interactions enough between nucleic particles to allow stability. I may never try to model nuclei in detail.

7. Explain gravity in electromagnetic terms. I believe gravity is part of a triumvirate of forces: electric, magnetic, and gravitational. Hence I would not get rid of it but it might be possible to explain gravity as an effect created by the presence of electric and/or magnetic energy. The fact that the Poynting (and velocity) vector of a photon is always in the direction of ExH, that a photon always moves at c in free space, and that it has energy and relativistic mass seem to be clues to the interrelationship between gravity and the other two forces. Gravity, in my opinion, might be modeled within the framework of a modified set of Maxwell's equations. But then, you would have to drop the quantum concept of force carrier virtual particles and revert to the use of field theories.

Quantum mechanics would survive as a very effective shorthand way of dealing with interactions between particles, but it would not play a significant role in defining the internal structure of particles.