In this paper we present a study of the beam-driven wave generation mechanisms in linear approximation which are viable in the flowside plasma mantle of Saturn's moon, Titan. The flowside plasma mantle is defined, by analogy with the dayside plasma mantle of the planet Venus and Mars, as being the interaction region between the cold ionospheric plasma and hot streaming plasma of magnetospheric or solar wind origin, with both types of plasma being present in comparable densities. Since no in situ plasma and field measurements are currently available in Titan's flowside mantle, we performed our model calculations in a broad plasma parameter space encompassing the plasma characteristics determined by Voyager 1 in Titan's wake. Two types of beam instability modes were found to be dominant: a fluid-like (nonresonant) modified two-stream instability (MTSI) and the kinetic (beam resonant) ion-ion acoustic instability (IIAI). The two instability modes are characterized by distinct frequency ranges (an order or below the lower hybrid frequency for the MTSI and a few times the lower hybrid frequency for the IIAI) and are found to be dominant in well-separated spatial regions determined by the presence/absence of cold ionospheric electrons. Giving a global rather than a specific description of the instability types expected to be the most important growing modes within Titan's flowside mantle, we intend to make predictions concerning the wave characteristics of the dominant wave modes measurable by the plasma wave instrument on board the Cassini spacecraft.