We present a feasible design concept and the science drivers for the proposed near-infrared interferometric integral field spectrograph at the LBT. Combining interferometric resolution with an integral field spectrograph is a very promising instrument concept for detailed studies down to below 10 mas angular resolution in the NIR. If approved, the instrument will become an extension to the LINC-NIRVANA instrument, which is under construction. In this contribution an opto-mechanical design concept has been studied in detail: that places the integral field unit into an existing empty compartment within the LINC hardware. Several optical and mechanical challenges have been successfully mastered, among them: - the limitation of the achievable angular resolution due to the parallactic angle rotation versus the LBT baseline, - the anamorphic magnification required by the LBT optics design to optimize the detector information content, and - integrating the IFU into the existing LINC cryostat without interfering with the existing optics and mechanics. The science program spans from solar system studies and spectroscopy of exoplanets to the black hole dynamics in the center of our and other galaxies.