Here we present a new approach for constraining luminous blazars, incorporating fully time-dependent and self-consistent modeling of bright gamma-ray flares of PKS1510-089 resolved with Fermi-LAT, in the framework of the internal shock scenario. The results of our modeling imply the location of the gamma-ray flaring zone outside of the broad-line region, namely around 0.3pc from the core for a free-expanding jet with the opening angle Gamma, \theta_\mathrm{jet} ≃ 1 (where Gamma is the jet bulk Lorentz factor), up to ≃ 3pc for a collimated outflow with Gamma, \theta_\mathrm{jet} ≃ 0.1. Moreover, under the Gamma, \theta_\mathrm{jet} ≃ 1 condition, our modeling indicates the maximum efficiency of the jet production during the flares, with the total jet energy flux strongly dominated by protons and exceeding the available accretion power in the source. This is in contrast to the quiescence states of the blazar, characterized by lower jet kinetic power and an approximate energy equipartition between different plasma constituents. We demostrate how strictly simultaneous observations of flaring PKS1510-089 at optical, X-ray, and GeV photon energies on hourly timescales, augmented by extensive simulations as presented in this paper, may help to impose further precise constraints on the magnetization and opening angle of the emitting region. Our detailed modeling implies in addition that a non-uniformity of the Doppler factor across the jet, caused by the radial expansion of the outflow, may lead to a pronounced time distortion in the observed gamma-ray light curves, resulting in particular in asymmetric flux profiles with substantially extended decay phases. ; Comment: 11 pages, 7 figures, accepted for publication in ApJ