The idea about leptons as local composites of 3 quarks (see this) is strongly suggested by the mathematical structure of TGD. Later it was realized that it is enough that leptons look like local composites in scales longer than CP2 scale defining the scale of the partonic 2-surface assignable to the particle.
The proposal has profound consequences. One might say that SUSY in the TGD sense has been below our nose for more than a century. The proposal could also solve matter-antimatter asymmetry since the twistor-lift of TGD predicts the analog of Kähler structure for Minkowski space and a small CP breaking, which could make possible a cosmological evolution in which quarks prefer to form baryons and antiquarks to form leptons.
The basic objection is that the leptonic analog of Δ might emerge. One must explain why this state is at least experimentally absent and also develop a detailed model. In the article Can one regard leptons as effectively local 3-quark composites? the construction of leptons as effectively local 3 quark states allowing effective description in terms of the modes of leptonic spinor field in H=M4× CP2 having H-chirality opposite to quark spinors is discussed in detail.
See the chapter The Recent View about SUSY in TGD Universe and the article Can one regard leptons as effectively local 3-quark composites?.