This study examined the effects of nature-friendly novel additives combination (metakaolin–bischofite-alkalinization, MkBA) on the mechanical and microstructural characteristics of laterite soil collected from Warangal, Telangana, India. Initial test results showed that the soil exhibited plastic behavior and did not possess adequate physical strength intended for use as dense subgrade materials in the virgin state. The characterizations used two mix-design proportions (MkBA1 and MkBA2) based on preliminary investigations. Uniaxial compressive strength (UCS) experiments were undertaken on the stabilized laterite soil to ascertain its suitability as a subgrade material based on the minimum standard requirements of different organizations. The effect of curing temperature was investigated on treated soil using a UCS sample by heating at 60 °C for 24 h for mix-design proportion with higher strength enhancement (i.e., MkBA2). XRD, FE-SEM, EDS, FTIR, and TGA/DTG tests were conducted on the optimum-designed sample for nano-structural assessment. In general, the research unveiled that the addition of the novel additive improved the mechanical strength of the soil and compact microstructure within a stabilized soil matrix. Furthermore, the heat-curing results of optimally treated samples (MKBAH2-3) showed a notable improvement in strength with an increment in value from 0.21 MPa in the unstabilized state to a peak value of 1.81, 2.27, and 2.67 MPa at 7-, 14-, and 28-day curing presets which is approximately 8.6, 10.8, and 12.7% times to virgin soil. From the UCS, it can be concluded that stabilized soil fulfills the minimum subgrade strength standards and specifications provided by different organizations. Finally, microstructural characterization reveals the formation of M-S-H, C(A)-S-H cementitious product.