  We put forward the framework of simplified leptoquark models: simple
extensions of the Standard Model that serve as benchmarks to test the
interactions of leptons with new colored degrees of freedom considered, for
instance, in leptoquark or grand unification models. As a first application of
the scheme, we analyze the power of precision lepton observables by computing
gauge invariant two-loop radiative corrections to the lepton-photon vertex,
generated here by Yukawa interactions between the lepton and new colored
degrees of freedom. The result, detailed in explicit expressions for the
involved form factors, improves on the literature for the higher loop order
considered and highlights the existence of regions in the parameter space of
the model where two-loop corrections cannot be neglected.
