Reusable is a lot more complex and given how the frontrunners themselves are struggling to build simple SSLV equivalents, VTVL vehicles are a far fetched dream for next 20 years from the private sector.
Everyone said the same of starship. Look where it is now. They achieved this feat in 10-12 years. Retiring scientists of ISRO who couldn’t try out their concepts due to lack of study approval or funds or time could work with startups for that. ISRO could work on Heavy Launch Vehicles, Actual science experiments, Human & Mars space programmes etc.
Agnikul engines are special in a sense, they can be printed easily & clustered. Dragon crew capsule was developed after NASA gave funding for both Boeing & SpaceX with expectations Boeing would succeed. ISRO could save valuable time by relegating such developments, launches to private companies. Leap of faith & money is required of course.
ISRO should quit itself from launching SSLV, PSLV by giving designs completely to private or let the users use their upcoming medium class launch vehicles, including lntegrstion and launch activities. We could concentrate on things which reallly are important