Most topological insulators suffer from intrinsically narrow band gaps, limiting their practical applications. Using tight-binding modeling and first-principles calculations, we show that in the topological state and band gap of the ferroelectric bilayer $\alpha \text{−}\mathrm{I}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_3$ ($2\mathrm{L}\text{−}\mathrm{I}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_3$) can be effectively tuned by controlling the hybridization strength $\left(V_{\text{hyb}}\right)$ between Se $p_x/p_y$ and $s/p_z$ orbitals through transition metal substitution at In sites. This mechanism is demonstrated in a $\mathrm{ScInS}{\mathrm{e}}_3/\mathrm{I}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_3$ van der Waals Heterostructure (vdWH), where enhanced charge transfer from Sc $d$ states to Se atoms strengthens the $\mathit{px}/\mathit{py}\text{−}s/\mathit{pz}$ orbitals' hybridization and enlarges the quantum spin Hall gap to 36 meV. Magnetic Cr substitution further yields a $\mathrm{CrInS}{\mathrm{e}}_3/\mathrm{I}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_3$ vdWH with a sizable $\sim 110$ meV quantum anomalous Hall gap and compressive strain-driven topological phase transitions—from a trivial magnetic insulator ($C=0$) to a Chern insulator ($C=1$), and finally, to a magnetic topological metal ($C=2$). These results establish a viable strategy for engineering band gaps and topological phases for low-power spintronic and quantum technologies.

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• Edge states
• Ferroelectricity
• Topological materials