We employ a simple field-theory model to explore the extent to which kinematical lightcone dominance entails also leading light-cone singularity dominance, for higher matrix elements of current products. We retain all leading logarithmic terms in the ladder approximation, and impose the Mueller-Regge picture as a boundary condition on simple two-particle matrix elements appropriate for processes such as massive lepton-pair production and semi-inclusive electroproduction. We explore several asymptotic regimes with current mass ${q}^{2}\ensuremath{\rightarrow}\ensuremath{\infty}$, and find that limit sequences may always be defined that become analytically equivalent to some leading-singularity limit, before any discontinuities are computed. This includes commutativity of the deep-Regge and deep-scaling limits, as suggested by Brandt and Preparata. In massive lepton-pair production the pionization (central) vertex ${V}_{P}({q}^{2}+{{q}_{\ensuremath{\perp}}}^{2}, {q}^{2})$ depends on the transverse momentum ${q}_{\ensuremath{\perp}}$ of the current, as well as the invariant mass ${q}^{2}$. In the present model, whenever ${q}^{2}\ensuremath{\rightarrow}\ensuremath{\infty}$ with $\frac{{{q}_{\ensuremath{\perp}}}^{2}}{{q}^{4}}$ finite, the appropriate residue in Mellin-transform space comes in part from the leading Mellin singularity relevant for the limit ${q}^{2}+{{q}_{\ensuremath{\perp}}}^{2}\ensuremath{\rightarrow}0$ in ${V}_{P}$, for the bremsstrahlung amplitudes. This suggests that perhaps any attenuation of these amplitudes, which carry the leading light-cone singularity, will not occur with emphasis on the ${q}^{2}+{{q}_{\ensuremath{\perp}}}^{2}$ scale in ${V}_{P}$ but rather on the second, independent ${q}^{2}$ scale. On the other hand, whenever ${q}^{2}\ensuremath{\rightarrow}\ensuremath{\infty}$ with $\frac{{{q}_{\ensuremath{\perp}}}^{2}}{{q}^{4}}\ensuremath{\rightarrow}\ensuremath{\infty}$, the appropriate residue in Mellin-transform space comes in part from the leading Mellin singularity relevant for the limit ${q}^{2}+{{q}_{\ensuremath{\perp}}}^{2}\ensuremath{\rightarrow}\ensuremath{\infty}$, for the bremsstrahlung amplitudes. The bremsstrahlung amplitudes are not attenuated in this limit, but rather develop a square root of a triple-Regge behavior. This behavior obtains only for the bremsstrahlung amplitudes, with the annihilation amplitudes becoming asymptotically independent of ${q}^{2}+{{q}_{\ensuremath{\perp}}}^{2}$. The existence of interpolating limits and nonattenuation of the bremsstrahlung amplitudes allows us to conclude that in the model no natural mechanism precludes dominance by the leading light-cone singularities, in any kinematically light-cone-dominated regime. In semi-inclusive electroproduction, the mechanism which generally links lightcone dominance with dominance by the leading light-cone singularity is graphically equivalent to the fixed-pole mechanism operating in inclusive electroproduction.