My favorite is the rishon model. Only two Weyl spinor fields (and 17 (8+8+1) associated massless gauge fields, based on a SU(3)xSU(3)xU(1) symmetry) are needed to describe the world of particles (without gravity). If one of them, call it C (with anti c) is electrically charged (1/3), and the other has zero electric charge (the rest being equal), call it Y (with anti u) then the particles of the standard model are:
Elektron: ccc
Up-quark: CCU
Down-quark: cuu
E. neutrino: UUU
Families are excitations of these bound states.
It's interesting to see what happens if we consider the electron, proton, neutron, and neutrino (which are universally present in a 1:1:1:1 ratio):
Electron: ccc
Proton: CCU CCU cuu
Neutron: CCU cuu cuu
Neutrino: UUU
What do we see? There are 6 C's and c's, and 6 U's and U's. Which means equal amounts of matter and antimatter! Which means that a version Wheeler's one-electron universe is applicable (and in this model a positron is indeed present in the proton as Wheeler hypothesized). The electron being a U or a C. Proton decay is "easily" explained (heuristically). In fact, ALL particle interactions could be.explained in this way .
Of course, there is no evidence that quarks or leptons are composite. But there is a lot of space left between the Planck scale and 10^-21m. Just smash two electrons head-on and listen if you hear a rattle within them. Or maybe the muon-g2 experiment is an expression of this theory. Or it is a fata morgana. Nature will tell us. I wonder how strong theory had to modified, if that could be done....
.